Email down again - Enter New password

I have been getting spurts of email outages with the message "Login to server imap.cox.net with user name xxxxxxx53 failed. I am give choice to retry, enter new password or cancel. I know the password is correct as I can log into webmail. However today even after logging into webmail I could get to my email list. I use Thunderbird and have used without problems for 5 years until the past month.

Marty