Hello @Timsgirll,
Not being able to log into your myATT app is disheartening to hear, as we don’t want our customers to be unable to access their accounts online. It will be my pleasure to help you.
Are you able to log into your myAT&T account on another device such as computer or tablet? If not, on the login page, please select Can’t remember User ID/Password and follow the prompts to fetch you User ID and reset your password.
If you are able to log in with a different device, on your phone, please go into Settings> Apps > Application Manager> All> myAT&T app> Clear Cache> Clear Data> Reboot phone and try again.
If the previous step didn’t work, please delete the app and then re-add it. You can get a step-by-step guide on how to delete and re-add the app at out Device Support Page. Please select your phone’s make and model> Tutorial> Apps & Web> Download apps & games.
Please let us know if these steps help! Have a wonderful day!
Katherine, AT&T Community Specialist