Enter your user name and password for the following server

Windows 11, Outlook 365. I have two email accounts, both with Google: mailto:email address removed for privacy reasons and the other mailto:email address removed for privacy reasons (Yes, it is a Google account since Telus farmed out its mail service to Google). I wanted mails from all accounts coming to my Inbox in Outlook, so I set both as POP. Everything was working just fine until recently I started receiving ‘Enter your user name and password for the following server’ message. This message refers always to mailto:email address removed for privacy reasons. It is very annoying since it pops up every few minutes. Searching for the solution I see that one needs to have 2-step verification to avoid this nuisance. But I already have 2-step verification enabled on both accounts since December 2022. Changing password does not help. I have tried several other suggestions, but nothing works. Is there any way of getting out of this, please?