Xfinity Connect email error: "...provided login data to access mail server imap.comcast.net seem to be wrong..."

I periodically get the pop-up error message on my Xfinity Connect browser-based email client (Window 10 Home, and Android), "Error The provided login data to access mail server imap.comcast.net seem to be wrong. Please correct them."  The problem is consistent across types of devices and various browsers.

I have gotten this error message for years, and I just dismiss it.  A half-hour later, it pops up again.  It would be nice, though, to actually fix the problem, if that is not too time-consuming. I will not call support on the phone because they have time-consuming protocols for the user to go through before they start to investigate the problem.