unable to log into email account from 3rd party email program

Two days ago, one of my comcast.net accounts encountered errors logging in on several third-party email programs. The email address was set up years ago under my main xfinity ID. Using either Thunderbird or the Android email default program I now get an error message that login fails with the username that I've always used.  Re-entering the password has no effect. I am still able to log in using a browser and see my emails. Moreover, under settings the check box is checked for allowing 3rd-party programs to access the email.

When I log into xfinity.com with my main ID, I don't see any secondary users. 

I have been using IMAP on Thunderbird. However, I set up a POP3 account and had the same error message.  

How can I fix this? I know that I can't set up a secondary user any more with their own email address. :(  I don't want to have to use a browser all the time to check email.