Unable to send/receive email on iPad mini 2 but can on iPhone 6

Both iPhone & iPad have successfully sent & received emails under same email account.  2 days ago, my iPad was unable to send & receive. The error message is —> “Cannot get email. The mail server “imap.mail.att.net” is not responding. Verify that you have entered the correct Account info in mail settings.”

I never touched the mail settings. But upon receiving the message, I verified that my email address was correct. I correctly re-entered my password. Contacted Apple & they couldn’t fix. What is your recommendation?  Thank you.