No gmail since yesterday

I have multiple POP accounts set up. They all worked fine until yesterday. Today, the three gmail accounts I have (1 @gmail, the others at organizations that use gmail) stopped working.

I updated K9 to the latest version and reapplied a new app password (generated by Google), but no luck. Other accounts continue to work fine on K9 (and all accounts work with Outlook).

Any idea what changed between yesterday and today and that gmail no longer works with K9? Anyone else experiencing the same? Any suggestions what I should try next?