My friend can't login with google

My friends account is basically blocked from being able to login, every time they log in, it gives an error saying to log in with google, but the account wasn't registered with google, so when they tried it, it created a new account with the google account. They can't access their servers because of this glitch, can someone please help? We have an smp on it that we've put many hours into, and we don't want to lose it all