Imap not working

One of the imap accounts I set up on k-9 doesn’t connect to the server anymore, the message says the authentication failed and to update server settings. But server settings are ok, they are the same as in Thunderbird on my laptop (which works fine). The “funny” thing is that I have two addresses on the same server (it’s an institutional one), both are imap, same settings (server, port, authentication…) and the second one works just fine and never had an issue.

I currently use version 6.711 but the issue started a few months ago after an update (whose version number I do not remember, unfortunately).

(on the side, I still have issues with a microsoft 365 account, but I guess this will be solved at some point, as it was on Thunderbird in version 115)