What version of ULib?
What version of ULX?
Do ULib and ULX show loading in the server console at server startup?
What errors show in server console at server start up?
You specifically mention gui... do other ULX commands work? (For instance, 'ulx who' from a game console, even non-admins will be able to see that in console)
What command(s) are you trying to get the gui and where?
When you run those commands, any error appear in server and or game console?