RETRY    ENTER A NEW PASSWORD  CANCEL.  

I have 3 e-mail accounts set up on my Thunderbird account 2 are sbcglobal e-mail accounts, and the other is a g-mail account. I had a problem several months ago with only one of my sbcglobal accounts where the "login to server imap.mail.net with username ..........@sbcglobal.net failed. I was asked to RETRY ENTER A NEW PASSWORD CANCEL. I tried several options, and finally had to pay someone to come and help me. He said I had to use a "SECURE MAIL KEY". He found that on our AT&T account. That e-mail is working now. The other day my '''2nd''' sbcglobal account stopped working and giving me the same error message "login to server imap.mail.net with username ..........@sbcglobal.net failed. I was asked to RETRY ENTER A NEW PASSWORD CANCEL. I have tried putting in the "SECURE MAIL KEY" that we used for the other e-mail, but it is not working with the 2nd account. My other sbcglobal account is working as is my g-mail. Please help! I can get into my 2nd email account on my phone, my tablet and with Microsoft Edge, so I don't know how to fix this... Please Help