java.lang.RuntimeException: An exception occurred when launching the server!
    at net.fabricmc.loader.impl.launch.server.FabricServerLauncher.main(FabricServerLauncher.java:68)
Caused by: java.lang.reflect.InvocationTargetException
    at java.base/jdk.internal.reflect.NativeMethodAccessorImpl.invoke0(Native Method)
    at java.base/jdk.internal.reflect.NativeMethodAccessorImpl.invoke(NativeMethodAccessorImpl.java:78)
    at java.base/jdk.internal.reflect.DelegatingMethodAccessorImpl.invoke(DelegatingMethodAccessorImpl.java:43)
    at java.base/java.lang.reflect.Method.invoke(Method.java:567)
    at net.fabricmc.loader.impl.launch.server.FabricServerLauncher.main(FabricServerLauncher.java:66)
Caused by: java.lang.RuntimeException: Error invoking MC server bundler: java.lang.UnsupportedClassVersionError: net/minecraft/bundler/Main has been compiled by a more recent version of the Java Runtime (class file version 61.0), this version of the Java Runtime only recognizes class file versions up to 60.0
    at net.fabricmc.loader.impl.game.minecraft.MinecraftGameProvider.processBundlerJar(MinecraftGameProvider.java:321)
    at net.fabricmc.loader.impl.game.minecraft.MinecraftGameProvider.locateGame(MinecraftGameProvider.java:206)
    at net.fabricmc.loader.impl.launch.knot.Knot.createGameProvider(Knot.java:172)
    at net.fabricmc.loader.impl.launch.knot.Knot.init(Knot.java:125)
    at net.fabricmc.loader.impl.launch.knot.Knot.launch(Knot.java:71)
    at net.fabricmc.loader.impl.launch.knot.KnotServer.main(KnotServer.java:23)
    ... 5 more
Caused by: java.lang.UnsupportedClassVersionError: net/minecraft/bundler/Main has been compiled by a more recent version of the Java Runtime (class file version 61.0), this version of the Java Runtime only recognizes class file versions up to 60.0
    at java.base/java.lang.ClassLoader.defineClass1(Native Method)
    at java.base/java.lang.ClassLoader.defineClass(ClassLoader.java:1010)
    at java.base/java.lang.ClassLoader.defineClass(ClassLoader.java:872)
    at net.fabricmc.loader.impl.game.minecraft.MinecraftGameProvider$1.loadClass(MinecraftGameProvider.java:277)
    at java.base/java.lang.ClassLoader.loadClass(ClassLoader.java:519)
    at java.base/java.lang.Class.forName0(Native Method)
    at java.base/java.lang.Class.forName(Class.java:466)
    at net.fabricmc.loader.impl.game.minecraft.MinecraftGameProvider.processBundlerJar(MinecraftGameProvider.java:297)
    ... 10 more
 

You'll have to ask the Fabric developers. Forge is a completely seperate project. We can't help you with issues caused by their tools.