GsmShield 2 issue

Gsm Shield 2 issue
New to arduino world and not an expert in the field... just a beginner but I'm not able to use gsm access with gsmAccess.begin method. I've tried all examples and suggestion found within the forum.
In any use case the method "gsmAccess.begin (PINNUMBER)" does not return anything and program did not go on....Can you suggest me something to try ? Sim works fine out of shied, no pin is configured. Modem test works properly but no way to connect to the network (send or receive sms, calls. Etc). Thanks a lot in advance.... fabrizio