Hello there @Needdata!
I’m sorry to hear you are encountering an error when trying to create an account. I am more than happy to assist you today!
Depending on your device the following process may vary, however our Device Support page does an exceptional job at guiding you through clearing the cache on apps. Once there, please select your device by manufacturer and model, and click on View All Solutions. Please direct your attention to the menu on the left and click on Troubleshooting. Lastly, select App Troubleshooting and follow the process to fix the myAT&T app.
If the above yields no results, there’s no need to worry. Please try setting your account up by using a desktop or laptop. Once the account is set up online; use those credentials to log into the mobile app.
Thank you for your time and letting me assist you. If you have any further questions please reach out to us in via Forums, we are here to help!
Cesar, AT&T Community Specialist