Webinar Error

In Webinar Practice Session, a Panelist signed out of their panelist account and signed into a personal account. When they tried to rejoin, they didn't get the normal attendee greeting that the Webinar would begin shortly. They got:

"Unable to join as panelist

If you were invited as a panelist to this webinar, please sign in to your account or join from the link in your email invitation."

And then no option to join the meeting as an attendee. There is no authentication required for this webinar, so we are worried some attendees won't be able to get in. Please advise. Is there an algorithm that notices their personal email is close to their panelist account or something?