Salve avevo problemi con il login post 1.03 e ho trovato il fix

If you have an authenticator and can't login, then you'll have to do what I'm having to do when this is happening. On the authenticator, choose Resync and wait until it says Sync Successful. If you can't login still, you may need to resync again.

The authenticator app seems incapable of keeping sync with the Blizz servers after the 1.03 patch. Until they address that issue, you may need to resync each time you attempt to login if your account is setup to prompt for authenticator code.