Hi
What kind of computer are you playing the game on.
What do you mean by unable to sign in?
Are you running the game through Steam?
Do you mean that you can't log into the games with your ID or that the game just doesn't load when you try and launch it?
If the games just don't launch when you try and load them, the first thing I'd do is try and reinstall them.
If you can't sign in to Steam, I'd try and check your Steam ID and password and see if they are correct by logging into your steam account.
Mike