Fabric 1.16.5
Fabric API: fabric-api-0.37.1+1.16
Scala Version: fabric-language-scala-1.0.0-fat

[13:13:13] [main/FATAL]: Failed to start the minecraft server
java.lang.RuntimeException: Could not execute entrypoint stage 'main' due to errors, provided by 'blockshifter'!
at net.fabricmc.loader.entrypoint.minecraft.hooks.EntrypointUtils.invoke0(EntrypointUtils.java:50) ~[fabric-server-launch.jar:?]
at net.fabricmc.loader.entrypoint.minecraft.hooks.EntrypointUtils.invoke(EntrypointUtils.java:33) ~[fabric-server-launch.jar:?]
at net.fabricmc.loader.entrypoint.minecraft.hooks.EntrypointServer.start(EntrypointServer.java:33) ~[fabric-server-launch.jar:?]
at net.minecraft.server.Main.main(Main.java:92) [intermediary-server.jar:?]
at jdk.internal.reflect.NativeMethodAccessorImpl.invoke0(Native Method) ~[?:?]
at jdk.internal.reflect.NativeMethodAccessorImpl.invoke(NativeMethodAccessorImpl.java:78) ~[?:?]
at jdk.internal.reflect.DelegatingMethodAccessorImpl.invoke(DelegatingMethodAccessorImpl.java:43) ~[?:?]
at java.lang.reflect.Method.invoke(Method.java:567) ~[?:?]
at net.fabricmc.loader.game.MinecraftGameProvider.launch(MinecraftGameProvider.java:234) [fabric-server-launch.jar:?]
at net.fabricmc.loader.launch.knot.Knot.launch(Knot.java:153) [fabric-server-launch.jar:?]
at net.fabricmc.loader.launch.knot.KnotServer.main(KnotServer.java:28) [fabric-server-launch.jar:?]
at jdk.internal.reflect.NativeMethodAccessorImpl.invoke0(Native Method) ~[?:?]
at jdk.internal.reflect.NativeMethodAccessorImpl.invoke(NativeMethodAccessorImpl.java:78) ~[?:?]
at jdk.internal.reflect.DelegatingMethodAccessorImpl.invoke(DelegatingMethodAccessorImpl.java:43) ~[?:?]
at java.lang.reflect.Method.invoke(Method.java:567) ~[?:?]
at net.fabricmc.loader.launch.server.FabricServerLauncher.launch(FabricServerLauncher.java:68) [fabric-server-launch.jar:?]
at net.fabricmc.loader.launch.server.FabricServerLauncher.setup(FabricServerLauncher.java:114) [fabric-server-launch.jar:?]
at net.fabricmc.loader.launch.server.FabricServerLauncher.main(FabricServerLauncher.java:56) [fabric-server-launch.jar:?]
Caused by: net.fabricmc.loader.api.EntrypointException: Exception while loading entries for entrypoint 'main' provided by 'blockshifter'
at net.fabricmc.loader.EntrypointStorage.lambda$getEntrypointContainers$1(EntrypointStorage.java:193) ~[fabric-server-launch.jar:?]
at net.fabricmc.loader.entrypoint.EntrypointContainerImpl.getEntrypoint(EntrypointContainerImpl.java:37) ~[fabric-server-launch.jar:?]
at net.fabricmc.loader.entrypoint.minecraft.hooks.EntrypointUtils.invoke0(EntrypointUtils.java:47) ~[fabric-server-launch.jar:?]
... 17 more
Caused by: java.util.ConcurrentModificationException
at java.util.HashMap.computeIfAbsent(HashMap.java:1225) ~[?:?]
at net.fabricmc.loader.EntrypointStorage$NewEntry.getOrCreate(EntrypointStorage.java:104) ~[fabric-server-launch.jar:?]
at net.fabricmc.loader.EntrypointStorage.lambda$getEntrypointContainers$1(EntrypointStorage.java:191) ~[fabric-server-launch.jar:?]
at net.fabricmc.loader.entrypoint.EntrypointContainerImpl.getEntrypoint(EntrypointContainerImpl.java:37) ~[fabric-server-launch.jar:?]
at net.fabricmc.loader.entrypoint.minecraft.hooks.EntrypointUtils.invoke0(EntrypointUtils.java:47) ~[fabric-server-launch.jar:?]
... 17 more

Could you please try again with v1.4.0 of the mod?
The crash message of the new version should be a bit more helpful.

Please comment if you are still having issues