Multimc Not loading

[firecactus3]

My minecraft wont launch in multimc this is my failed to start part of the log

 

Minecraft process ID: 7244

Using onesix launcher.

Failed to start Minecraft:
java.lang.reflect.InvocationTargetException
    at java.base/jdk.internal.reflect.DirectMethodHandleAccessor.invoke(DirectMethodHandleAccessor.java:110)
    at java.base/java.lang.reflect.Method.invoke(Method.java:578)
    at org.multimc.onesix.OneSixLauncher.launchWithMainClass(OneSixLauncher.java:210)
    at org.multimc.onesix.OneSixLauncher.launch(OneSixLauncher.java:245)
    at org.multimc.EntryPoint.listen(EntryPoint.java:143)
    at org.multimc.EntryPoint.main(EntryPoint.java:34)
Caused by: java.lang.ClassCastException: class jdk.internal.loader.ClassLoaders$AppClassLoader cannot be cast to class java.net.URLClassLoader (jdk.internal.loader.ClassLoaders$AppClassLoader and java.net.URLClassLoader are in module java.base of loader 'bootstrap')
    at net.minecraft.launchwrapper.Launch.<init>(Launch.java:34)
    at net.minecraft.launchwrapper.Launch.main(Launch.java:28)
    at java.base/jdk.internal.reflect.DirectMethodHandleAccessor.invoke(DirectMethodHandleAccessor.java:104)
    ... 5 more
Exiting with -1
Process exited with code -1 (0xffffffffffffffff).
Please note that usually neither the exit code, nor its description are enough to diagnose issues!
Always upload the entire log and not just the exit code.
 

[RoboPhilip]

I am having similar problems, but t is launching. My problem is that, while everything else is working fine, when i launch Minecraft through multimc, none of the mods i installed take effect. I have mods like immersive portals, buildcraft, etc, and what i end up playing is vanilla Minecraft. I am not sure if it is because i use linux Ubuntu, but it should be working. I did all the steps correctly, i hope, and none of the mods are working. What should i do?

[warjort]

Issues with your launcher should be reported to them.

If you really suspect the problem is with forge, you need to provide the logs/debug.log so we can see what is happening.