Having trouble opening the forge .jar file

I recently tried hosting a forge server as a localhost server for myself, but ran into some trouble.
When I downloaded the server pack of the modpack I wanted a server of ("The 1.12.2 pack Perfectly Complex") and all seemed to work fine, set up the minecraft server, world etc...
But when I tried getting the modded server version running by starting the forge jar, it didn't really do much. I then ran the Launch server bat they had included in the server pack and it gave me this error message stuff :

A problem occurred running the Server launcher.java.lang.reflect.InvocationTargetException
   at java.base/jdk.internal.reflect.NativeMethodAccessorImpl.Invoke0(Native Method)
   at java.base/jdk.internal.reflect.NativeMethodAccessorImpl.Invoke(NativeMethodAccessorImpl.java:77)
   at java.base/jdk.internal.reflect.DelegatingMethodAccessorImpl.Invoke(DelegatingMethodAccessorImpl.java:43)
   at java.base/java.lang.reflect.Method.invoke(Method.java:568)
   at net.minecraftforge.fml.relauncher.ServerLaunchWrapper.run(ServerLaunchWrapper.java:70)
   at net.minecraftforge.fml.relauncher.ServerLaunchWrapper.main(ServerLaunchWrapper.java:34)
Caused by: java.lang.ClassCastException: class jdk.internal.loader.ClassLoaders$AppClassLoader cannot be cast to class java.net.URLClassLoader (jdk.internal.loader.ClassLoader$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)
   ... 6 more
Press any key to continue . . .

I don't really know what to do with that.

I reinstalled java (java 8_321)
Installed forge (forge-1.12.2-14.23.5.2860)
and tried running it again, still nothing really happening.

At this point I don't know if I'm just to stupid to get it running or if there is actually a problem with the jar.