No need to remove the account, but you should change the authentication method on the incoming and outgoing to OAuth2, if it's currently 'normal password'. Remove the passwords from Saved Passwords in Preferences, and in the same section accept cookies. Then, restart TB and enter the account password in the OAuth window to allow TB access.

I am still having trouble. I am not the sharpest tool in the shed unfortunately. I'm too old for change :) So I went through AOL and changed my password and I now have these settings on Outgoing Mail- smtp.aol.com, port 465, my email address the OAuth2 and SSL/TLS and that seems to work fine for outgoing mail. However I cannot RECEIVE mail now. On Server Settings I have imap@aol.com, Port 993, my email address then SSL/TLS and OAuth2 and I keep getting 'Error POP3 Mail Server imap@aol.com responded"

If you can please help me you would make an old man really happy. Thank you!

The error says you're trying to connect to a POP server imap.aol.com, but the correct POP server is pop.aol.com. It looks like you tried to change from POP to IMAP by just changing the server from pop.aol.com to imap.aol.com. To make the change, the IMAP account has to be added as a new account, starting from File/New/Existing Mail Account. But if you really want POP access, change the setting from imap.aol.com on 993 to pop.aol.com on 995. In the Server Settings section, Server Type is shown at the top.

http://kb.mozillazine.org/Convert_a_POP_account_to_a_IMAP_account

I got it working with the pop address. Thank you I hope I never have to change anything again.