If you have an account on AT&T Mail and see that ATT mail not working, first, check if the device you are using is connected to the internet. If there’s no issue with the internet, you can follow the below-mentioned troubleshooting steps:
For computers, check if the LAN cable is connected to your computer and the router or your modem is connected properly.
Replace the LAN cable if required.
For wireless internet connection, ensure that your device is connected to the wireless network. Check if you can browse other websites.
Ensure that the email username and password you’ve entered are correct.