Hey
Documentation for plugins: Plugins in Unreal Engine | Unreal Engine 5.1 Documentation
UBlueprintFunctionLibrary should be used as base for class that is never instanced and holds only static (blueprintcallable) functions.
It is often very helpful to see log output. It can be found in "\Saved\Logs" or can be enabled with “showlog” command (in game, after “~” is pressed) or -log commandline switch.
Cheers,
M