why does my GPS not work in Italy without WiFi?
The GPS should eventually work without wifi, the further you are in distance and time from the last GPS sync, the longer the startup time will be.   Perhaps in Slovenia and Croatia you used it enough that the startup time was reasonable.  (Wifi access can shortcut the process by giving the GPS a hint as to your probably location).

I would suggest putting the tablet somewhere stationary with a clear view of the sky and giving it a good while to sync, it will probably eventually sync up.