Unable to login to IMAP account using Mac Mail

Woke up today to discover that I am unable to retrieve my email using the Mail app on any of my devices (iMac, iphone, ipad). Used Mail Connection Doctor and it says that the login of IMAP account failed and to verify the username and password. I know the problem is not my account id and password since I can access my email using web browser. The SMTP connected and is working fine.

The details from Mail Connection Doctor reveal:

READ Feb 17 12:27:26.154 [kCFStreamSocketSecurityLevelTLSv1_0] -- host:imap.mail.att.net -- port:993 -- socket:0x7ff14473b3b0 -- thread:0x7ff1456a1230

4.37 NO [AUTHENTICATIONFAILED] AUTHENTICATE Invalid credentials

WROTE Feb 17 12:27:26.154 [kCFStreamSocketSecurityLevelTLSv1_0] -- host:imap.mail.att.net -- port:993 -- socket:0x7ff14473b3b0 -- thread:0x7ff1456a1230

5.37 AUTHENTICATE PLAIN (*** 52 bytes hidden ***)

Can anyone offer suggestions?