Forge 1.12.2-14.23.5.2855 Not Working For Server

Hi, trying to run this gives me this message and instantly closes:

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:62)
        at java.base/jdk.internal.reflect.DelegatingMethodAccessorImpl.invoke(DelegatingMethodAccessorImpl.java:43)
        at java.base/java.lang.reflect.Method.invoke(Method.java:566)
        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$AppClassLoader cannot be cast to class java.net.URLClassLoader (jdk.internal.loader.ClassLoaders$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)
        ... 6 more

and here's the crash report:

[18:46:49] [Server thread/INFO]: Starting minecraft server version 1.12.2
[18:46:49] [Server thread/INFO]: Loading properties
[18:46:49] [Server console handler/ERROR]: Exception handling console input
java.io.IOException: The handle is invalid
    at java.io.FileInputStream.readBytes(Native Method) ~[?:?]
    at java.io.FileInputStream.read(FileInputStream.java:271) ~[?:?]
    at java.io.BufferedInputStream.read1(BufferedInputStream.java:282) ~[?:?]
    at java.io.BufferedInputStream.read(BufferedInputStream.java:343) ~[?:?]
    at sun.nio.cs.StreamDecoder.readBytes(StreamDecoder.java:297) ~[?:?]
    at sun.nio.cs.StreamDecoder.implRead(StreamDecoder.java:339) ~[?:?]
    at sun.nio.cs.StreamDecoder.read(StreamDecoder.java:188) ~[?:?]
    at java.io.InputStreamReader.read(InputStreamReader.java:178) ~[?:?]
    at java.io.BufferedReader.fill(BufferedReader.java:161) ~[?:?]
    at java.io.BufferedReader.readLine(BufferedReader.java:329) ~[?:?]
    at java.io.BufferedReader.readLine(BufferedReader.java:396) ~[?:?]
    at nz$2.run(SourceFile:100) [minecraft_server.1.12.2.jar:?]

Was wondering if anyone could help me fix this? Cheers

EDIT: I'm using this version for a modpack that is 14.23.5.2838, but the installer for that version won't open at all

Edited September 10, 20214 yr by ColourMeGreen
Missing information