Many plugins and mods build on others: a shop plugin needs Vault and an economy plugin, a menu plugin needs PlaceholderAPI, a Fabric mod needs Fabric API. If this foundation is missing, too old, or fails to start itself, the dependent plugin shuts down completely or partially. In most cases the server keeps running, only the features of the affected plugin are missing.

Each section below covers one message. You can find the full message in the Console or under Files in logs/latest.log. Also read the lines before it, as they often show which plugin failed first. Before you swap plugins or change configuration files, create a backup under Backups. After every change, restart the server completely instead of using /reload, so that all plugins load in the correct order.

A class is missing: NoClassDefFoundError and ClassNotFoundException

What the message looks like:

java.lang.NoClassDefFoundError: org/cloudburstmc/math/GenericMath
	at <Plugin>.jar//org.cloudburstmc.math.vector.Vector3i.from(Vector3i.java:403)
Caused by: java.lang.ClassNotFoundException: <Package>.<Class>

What is behind it: Plugins and mods for Java servers consist of many classes, which are individual building blocks of the program. The message says: a plugin or mod wants to use a building block that does not exist on the server. Usually another mod or plugin is missing, or it is installed in a version that does not contain this building block or no longer does. The rest of the server generally keeps running, only the affected feature fails.

How to fix it:

  1. Find out who is throwing the error. The plugin name after to in the line "Could not pass event … to …" or the file name before .jar// in the stack trace, that is, in the at … lines below the message, will tell you.
  2. Read the missing class path. Its beginning often names the project it belongs to, such as org/geysermc for Geyser.
  3. On the page of the affected plugin or mod, compare the required dependencies and versions with your installed Plugins or Mods.
  4. Install missing dependencies or bring everything involved to matching versions. Then restart the server.

Good to know: If a plugin file was replaced while the server was running, the plugin often can no longer find its own classes. In that case a full restart is enough.

A command doesn't work because its plugin is disabled

What the message looks like:

Unexpected exception while parsing console command "<Command>"
org.bukkit.command.CommandException: Cannot execute command '<Command>' in plugin <Plugin> v<Version> - plugin is disabled.

What is behind it: The command itself is not wrong. It belongs to a plugin that could not be enabled at server startup, so the server answers with this error every time it is called. The actual reason is written higher up in the log at startup, often "unsupported server version": the plugin version does not match your server version. If the plugin replaces basic commands such as list, as EssentialsX does, those fail too.

How to fix it:

  1. Under Files, open logs/latest.log and search for the plugin name from the message. The lines from the startup phase are important, such as "Error occurred while enabling …".
  2. Enter plugins in the Console. Disabled plugins appear in red there.
  3. Fix the startup error. Usually you install a version under Plugins that matches your server version. You can see your server version under Version. More on this: Plugin doesn't match the server version.
  4. Restart the server and use plugins to check whether the plugin is now green.

Good to know: The command message is only a consequence. It disappears as soon as the plugin starts again.

Vault or an economy plugin is missing

What the message looks like:

[<Plugin>] Vault economy not found! Disabling plugin...
[<Plugin>] - Disabled due to no Vault dependency found!

What is behind it: Plugins that handle money, prices, or bounties do not manage balances themselves. They access an economy plugin through Vault. Vault is only the interface, the accounts are kept by the economy plugin. If either of the two is missing or was only loaded after the dependent plugin, the latter shuts down. The server keeps running, but the affected plugin is missing entirely.

How to fix it:

  1. Check under Plugins whether Vault is installed.
  2. Check whether an economy plugin with Vault support is installed, for example EssentialsX with EssentialsX Economy, CMI, or XConomy.
  3. Install whatever is missing, in each case in a version for your server version.
  4. Restart the server completely. A /reload or reloading individual plugins easily messes up the load order.
  5. Enter vault-info in the Console. Your economy plugin should now appear after "Economy".

Good to know: The message also appears when Vault is present but the economy plugin itself fails at startup. In that case, search logs/latest.log for its name.

Plugin cannot register parts because another plugin is missing

What the message looks like:

[<Plugin>] Failed to register events for class <Class> because me/clip/placeholderapi/<Class> does not exist.
[QuickShop-FindItemAddOn] Uh oh! Looks like either this plugin has crashed or you don't have QuickShop-Hikari installed.

What is behind it: At startup, a plugin registers its listeners, which are the parts that react to events such as joining, breaking, or buying. Some of them require another plugin. If it is missing, exactly those parts are not registered, while the rest of the plugin runs. The path after because reveals which plugin is missing:

  • me/clip/placeholderapi belongs to PlaceholderAPI
  • net/milkbowl/vault belongs to Vault
  • com/ghostchu/quickshop belongs to QuickShop-Hikari
  • net/ess3 belongs to EssentialsX

How to fix it:

  1. Match the path from the message to a plugin using the list above. For other paths, the project name in the path helps, such as com/projectkorra for ProjectKorra.
  2. Install the missing plugin under Plugins in a version for your server version.
  3. Restart the server and check whether the message no longer appears on startup.

Good to know: If the path begins with io/papermc or org/bukkit, no plugin is missing. In that case your server software is too old for the plugin or the wrong software is running, for example Spigot instead of Paper. Help with this: Plugin doesn't match the server version.

A plugin cannot connect to another plugin

What the message looks like:

[<Plugin>] Could not hook into PlaceholderAPI!
<Plugin> will now disable!

What is behind it: "Hook" means a connection here. The reporting plugin wanted to connect to another plugin at startup that it needs to work. That plugin was either missing or not yet loaded at that point. Many plugins then shut themselves down. The server keeps running normally, but the features of the reporting plugin are missing entirely, so for a menu plugin that means all menus.

How to fix it:

  1. Read both names from the message: the reporting plugin in square brackets, the missing one after "hook into".
  2. If the missing plugin is not listed under Plugins, install it in a version for your server version. Very often it is PlaceholderAPI.
  3. If it is already installed, search logs/latest.log for its name. If it throws an error at startup itself, that is the actual cause. Fix that first.
  4. Restart the server completely.

Good to know: You do not need to reinstall the reporting plugin. It works again as soon as the dependency is available at startup.

ViaBackwards shuts down because ViaVersion is too old

What the message looks like:

[ViaBackwards] YOUR VIAVERSION IS OUTDATED
[ViaBackwards] VIABACKWARDS WILL NOW DISABLE

What is behind it: ViaVersion lets players with newer Minecraft versions onto your server, and ViaBackwards adds the same for older versions. ViaBackwards is an extension of ViaVersion and requires a matching, sufficiently recent ViaVersion build. If ViaVersion is older, ViaBackwards shuts down. The server keeps running, but players with older clients can then no longer get in.

How to fix it:

  1. Check under Plugins which versions of ViaVersion and ViaBackwards are installed.
  2. Update both together to current builds that match each other. The message itself names the official download page. If you also use ViaRewind, update it in the same step.
  3. Restart the server and use plugins in the Console to check whether ViaBackwards appears green.

Good to know: Always update the Via plugins together. If you only renew ViaBackwards, you end up with exactly this message.

In detail: Setting up ViaVersion: connecting older and newer clients

UltimateDonutSmp shuts down without PlaceholderAPI

What the message looks like:

[UltimateDonutSmp] UltimateDonutSmp requires PlaceholderAPI
[UltimateDonutSmp] UltimateDonutSmp is disabling itself to prevent broken sidebar output.

What is behind it: UltimateDonutSmp shows values in the sidebar, the display on the right edge of the screen. These values come through placeholders, small variables such as %player_name%, which PlaceholderAPI fills with real values. If PlaceholderAPI is missing or disabled, UltimateDonutSmp deliberately shuts itself down so that players do not see broken placeholders. The server itself keeps running normally.

How to fix it:

  1. Install PlaceholderAPI under Plugins in a version for your server version.
  2. If it is already installed, check in logs/latest.log whether it throws an error at startup, and fix that first.
  3. Stop the server and then start it again. Reloading with a command is not enough here.

Good to know: If the sidebar then shows text such as %vault_eco_balance% instead of numbers, an expansion for PlaceholderAPI is missing. You download it in the Console with papi ecloud download <Expansion> and apply it with papi reload.

A required plugin is not installed

What the message looks like:

[<Plugin>] <Dependency> is required but was not found
[<Plugin>] <Dependency> plugin not found! Disabling
[<Plugin>] Download <Dependency> from https://<Address>

What is behind it: The plugin builds on another plugin and cannot find it at startup. The message itself names this foundation, sometimes even with a download address. Depending on the plugin, it shuts down completely or part of it does not work. The message also appears if the foundation is present as a file in the plugins folder but fails to start itself.

How to fix it:

  1. Note the name of the missing foundation from the message.
  2. Check under Plugins whether it is installed. If not, install it in a version that matches your server version. Here is how: Installing and managing plugins.
  3. If it is installed, search logs/latest.log for its name. An error at startup is then the actual cause.
  4. Restart the server.

Good to know: If you no longer need the reporting plugin at all, you can remove it instead. The message then disappears too.

A plugin cannot find an economy system

What the message looks like:

[<Plugin>] Vault economy provider not found!
[<Plugin>] Vault is not found or no economy plugin found

What is behind it: For money, prices, and rewards, the plugin needs two partners: Vault or VaultUnlocked as the interface and an economy plugin such as EssentialsX that keeps the account balances. If it does not find both, it shuts down or does not hand out money rewards. Typical consequences: a shop plugin like QuickShop does not start properly, a quest plugin reports that it cannot pay out a reward.

How to fix it:

  1. Check under Plugins whether Vault or VaultUnlocked is installed.
  2. Check whether an economy plugin is running, for example EssentialsX. Without such a plugin, Vault has nothing it can pass on.
  3. Install whatever is missing, in versions for your server version, and restart the server.
  4. For Vault, use vault-info in the Console to check whether an economy plugin appears after "Economy".

Good to know: How to set up EssentialsX is explained in Setting up EssentialsX.

The bounty plugin Bountys doesn't find Vault

What the message looks like:

[Bountys] Vault Plugin wasn't detected!

What is behind it: Bountys pays out bounties through Vault and, for that, usually also needs an economy plugin that keeps the account balances. At startup, Vault was not found. As a result, the money features of Bountys do not work, so bounties cannot be paid out. The server itself and other plugins are not affected.

How to fix it:

  1. Decide whether you need Bountys. If not, remove it under Plugins and the message is gone.
  2. If you want to keep it, put Vault and a compatible economy plugin such as EssentialsX into the plugins folder, most easily via Plugins.
  3. If Vault is already there, check in logs/latest.log whether Vault itself reports an error at startup.
  4. Restart the server and use vault-info in the Console to check whether Vault has found an economy plugin.

Good to know: If other plugins also report that Vault or an economy is missing, you fix all the messages with the same step.

AuthMe finds no permissions plugin through Vault

What the message looks like:

[AuthMe] Error while hooking into Vault [PermissionHandlerException]: Could not load permissions provider service

What is behind it: AuthMe is a login plugin where players sign in with a password. For its group and permission features, it asks Vault for a permission service, that is, a permissions plugin. Vault is installed, but it does not provide AuthMe with such a service. As a result, the group and permission features of AuthMe fail. The message only affects these additional features.

How to fix it:

  1. Under Plugins, install LuckPerms or another permissions plugin with Vault support.
  2. Update Vault and AuthMe to versions for your server version.
  3. Restart the server.
  4. Enter vault-info in the Console. Your permissions plugin should now appear after "Permission".

Good to know: How to create groups and permissions is shown in Setting up LuckPerms.

StackSpawners needs DecentHolograms

What the message looks like:

[StackSpawners] DecentHolograms was not found. The plugin will not work

What is behind it: StackSpawners merges spawners and uses the plugin DecentHolograms for its floating displays, so-called holograms. It does not include this feature itself. If StackSpawners does not find DecentHolograms at startup, it cannot work. The server keeps running, but the features of StackSpawners are missing.

How to fix it:

  1. Install DecentHolograms under Plugins in a version that matches your server version and StackSpawners. The plugin page of StackSpawners lists the supported versions.
  2. If DecentHolograms is already there, search logs/latest.log for a startup error from DecentHolograms and fix it first.
  3. Stop the server completely and start it again. This way both plugins load in the correct order.

Good to know: If you no longer use StackSpawners, remove it. The dependency then goes away as well.

LightAntiCheat-Plus doesn't find PacketEvents

What the message looks like:

(LightAntiCheat-Plus) Failed to start listener-mode … com/github/retrooper/packetevents/event/PacketListenerCommon

What is behind it: LightAntiCheat-Plus is an anti-cheat plugin. It reads the players' data traffic through PacketEvents, a separate plugin that prepares network packets for other plugins. If PacketEvents is missing or installed in a version that LightAntiCheat-Plus does not expect, its monitoring does not start. The server keeps running, but cheat protection is then fully or partially off.

How to fix it:

  1. Check on the LightAntiCheat-Plus page which PacketEvents version it needs.
  2. Install or update PacketEvents under Plugins to that version, matching your server version.
  3. If needed, also update LightAntiCheat-Plus so that both match each other.
  4. Stop the server completely and restart it.

Good to know: Other plugins often use PacketEvents as well. After the change, check in logs/latest.log whether they continue to start without errors.

A plugin shut itself down after an error

What the message looks like:

[<Plugin>] An unexpected error occurred, disabling the plugin
[<Plugin>] Cannot enable plugin: <Reason>

What is behind it: The plugin ran into an error at startup or during operation and therefore shut itself down. Until the next restart, all of its features are missing, and its commands only answer with an error message. Which plugin is affected is shown in square brackets. The cause is usually in the lines before it, and depending on the plugin's origin, possibly in another language.

How to fix it:

  1. Open logs/latest.log and read the lines directly before the message. A missing plugin, a mismatched version, or an error in the configuration can usually be spotted there.
  2. Update the plugin and check on its page whether it matches your server version.
  3. If the error remains, remove the plugin as a test and restart. If everything runs without it, report the error to the plugin author and attach the lines from the log.

Good to know: You can sort out errors during operation with Plugin throws errors during operation.

AuthMeBia doesn't match your AuthMe version

What the message looks like:

[AuthMeBia] AuthMe DataSource reflection unavailable; premium skip and session autologin both disabled

What is behind it: AuthMeBia is an extension for the login plugin AuthMe. It accesses a function inside AuthMe that does not exist in that form in your AuthMe version. As a result, AuthMeBia disables two features: premium skip, which lets players with a purchased Minecraft account in without a password, and session autologin, the automatic login when someone rejoins shortly after leaving. AuthMe itself keeps working, and players then log in with a password as usual.

How to fix it:

  1. Check under Plugins which versions of AuthMe and AuthMeBia are installed.
  2. On the AuthMeBia page, check which AuthMe version it was built for.
  3. Update both to matching versions and restart the server.
  4. Test with a purchased account whether joining without a password works again.

A ProjectKorra addon doesn't match the main version

What the message looks like:

java.lang.NoSuchMethodError: 'void com.projectkorra.projectkorra.<Class>.<Method>()'
com.jedk1.jedcore.ability.<Ability>@<Identifier>[…]

What is behind it: ProjectKorra brings bending abilities to the server, and addons such as JedCore add more. Each addon is built for a specific ProjectKorra version. If it calls a method, that is, a function that does not exist in your ProjectKorra version, it aborts with "NoSuchMethodError". Sometimes it also writes the state of an ability as a long line into the log. The affected abilities then do not work, while the rest of the server keeps running.

How to fix it:

  1. Under Plugins, note the version of ProjectKorra and the versions of all addons.
  2. Open the download page of each addon. It states which ProjectKorra version it needs.
  3. Install ProjectKorra and all addons in versions that match each other and your server version.
  4. Restart the server and test an ability from the addon.

Good to know: If an addon does not exist for your ProjectKorra version, it is better to remove it than to mix old and new versions.

AppleSkin doesn't start because Fabric API is missing

What the message looks like:

Mod 'AppleSkin' (appleskin) <Version> requires any version of fabric-api, which is missing!

What is behind it: Most Fabric mods need the Fabric API library, a collection of shared building blocks that is not part of the Fabric Loader itself. AppleSkin is installed, but Fabric API is not. The Fabric Loader checks this at startup and aborts it. Your server therefore only starts again once you add Fabric API or disable AppleSkin.

How to fix it:

  1. Under Mods, install Fabric API in the version for your Minecraft version.
  2. If you do not need AppleSkin, use the repair button next to the message in the Server health view instead. It disables AppleSkin (the file is kept) and restarts the server.
  3. Check in the Console whether the server starts up completely.

Good to know: Fabric API must match your Minecraft version. The message says "any version", so AppleSkin itself does not impose any special requirement.

In detail: Fabric Loader and Fabric API: Resolving version errors precisely

Your message isn't listed?

Read the whole message in logs/latest.log, including the lines before it. The server usually names the plugin that failed first, and only afterwards the follow-up errors of other plugins. In the stack trace, the file names before .jar and the folder names in the class path, such as me/clip/placeholderapi, reveal which plugin or mod is involved. Then compare the dependencies on the project page with your installed plugins. Create a backup before every change. If you get stuck, open a ticket and include the time of the message.