If you created your Tandem account using the Facebook login method, make sure you are logged into the correct Facebook account on both your Facebook mobile app and in your mobile browser app (Safari, Google Chrome, etc.). Then tap “Facebook” on our login screen and you will successfully be logged back in. If you are still having problems, please try a different login method or contact us with your Tandem ID or email address and we can double-check your login method for you.