Feed the beast Modpacks are not launching.?

I'm launching from twitch, and the minecraft launcher appears, but I get this error: Java HotSpot(TM) 64-Bit Server VM warning: Ignoring option PermSize; support was removed in 8.0 Exception in thread "main" java.lang.ClassCastException: class jdk.internal.loader.ClassLoaders$AppClassLoader cannot be... show more I'm launching from twitch, and the minecraft launcher appears, but I get this error:
Java HotSpot(TM) 64-Bit Server VM warning: Ignoring option PermSize; support was removed in 8.0
Exception in thread "main" java.lang.ClassCastException: class jdk.internal.loader.ClassLoaders$AppClas... cannot be cast to class java.net.URLClassLoader (jdk.internal.loader.ClassLoaders$AppCla... and java.net.URLClassLoader are in module java.base of loader 'bootstrap')
at net.minecraft.launchwrapper.Launch.<init...
at net.minecraft.launchwrapper.Launch.main(...
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