I set NetworkManager->VPN Name->Advanced->Use Point-to-Point Encryption (MPPE) from 'All Available (default)' to '128-bit (most secure)', which fixed the login issue for me...
I set NetworkManager->VPN Name->Advanced->Use Point-to-Point Encryption (MPPE) from 'All Available (default)' to '128-bit (most secure)', which fixed the login issue for me...