Pixelmon Startup failing

Technical Support
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1

OS Name/Version: Ubuntu Server 24.04.2

Product Name/Version: AMP Release “Phobos” v2.6.1.2

Problem Description: The startup fails within 5 seconds of pushing start. And I’ve tried the different available Java settings and no other versions of Java works.

WARNING: An illegal reflective access operation has occurred
WARNING: Illegal reflective access by cpw.mods.modlauncher.SecureJarHandler (file:/home/amp/.ampdata/instances/Pixelmon01/Minecraft/libraries/cpw/mods/modlauncher/8.1.3/modlauncher-8.1.3.jar) to field java.util.jar.Manifest.jv
WARNING: Please consider reporting this to the maintainers of cpw.mods.modlauncher.SecureJarHandler
WARNING: Use --illegal-access=warn to enable warnings of further illegal reflective access operations
WARNING: All illegal access operations will be denied in a future release
Exception in thread "main" java.lang.UnsupportedClassVersionError: net/jomcraft/jcplugin/JCPlugin has been compiled by a more recent version of the Java Runtime (class file version 60.0), this version of the Java Runtime only recognizes class file versions up to 55.0

Steps to reproduce:

  • Install the server
  • Add the mods
  • Start the server

Actions taken to resolve so far: Tried using different Java versions and nothing worked.

2

You need to select the correct Java version. Java 16 or newer needs to be selected.

3

I only have java 8, 11, 17, and 21

4

Then set it to 21, that’s newer than 16.

5

I tried 21 also and it didnt work aswell. I stopped the server and updated it and started and got the same error.

6

Show me the error you get when its set to 21.

7 
Exception in thread "main" java.lang.IllegalAccessError: class cpw.mods.modlauncher.SecureJarHandler (in unnamed module @0x6107227e) cannot access class sun.security.util.ManifestEntryVerifier (in module java.base) because module java.base does not export sun.security.util to unnamed module @0x6107227e
	at cpw.mods.modlauncher.SecureJarHandler.lambda$static$1(SecureJarHandler.java:45)
	at cpw.mods.modlauncher.api.LamdbaExceptionUtils.uncheck(LamdbaExceptionUtils.java:95)
	at cpw.mods.modlauncher.SecureJarHandler.<clinit>(SecureJarHandler.java:45)
	at cpw.mods.modlauncher.Launcher.lambda$new$6(Launcher.java:55)
	at java.base/java.util.concurrent.ConcurrentHashMap.computeIfAbsent(ConcurrentHashMap.java:1708)
	at cpw.mods.modlauncher.api.TypesafeMap.computeIfAbsent(TypesafeMap.java:52)
	at cpw.mods.modlauncher.api.TypesafeMap.computeIfAbsent(TypesafeMap.java:47)
	at cpw.mods.modlauncher.Environment.computePropertyIfAbsent(Environment.java:62)
	at cpw.mods.modlauncher.Launcher.<init>(Launcher.java:55)
	at cpw.mods.modlauncher.Launcher.main(Launcher.java:66)
	at net.minecraftforge.server.ServerMain$Runner.runLauncher(ServerMain.java:63)
	at net.minecraftforge.server.ServerMain$Runner.access$100(ServerMain.java:60)
	at net.minecraftforge.server.ServerMain.main(ServerMain.java:57)
8

You could try using Java 17, or check that you have the right version of the jomcraft/jcplugin mod