it’s a temporary checkmark introduced after the outage to ramp up in stages - and not very publicised sadly.
As to OAuth - I guess this is the culprit.
The tokens can expire when the renewal didn’t take place. Both of you in this thread said previously that the message multiple_ecloud_account_not_permitted_message (in your translation, introduced a long time ago) will show up on that flow. Is this still the case if you do the re-auth from that settings menu shown in the Screenshot?
Edit: can’t get my murena account (when re-adding) to use an OAuth flow instead of user+pass. I see murena is back at migrating to OIDC. Maybe my murena-ID isn’t eligible. Can’t reproduce that way