@jane-n Glad to hear that, my bad then.
I have tried to use different windows (private and not) and tabs, different browsers (Vivaldi, Firefox, Edge) on two different PCs and a mobile phone (Vivaldi). I also have tried to clean cookies between session. The effect is stil the same: I can log in to my private account but not to the official one, with the same screen showing up on each try, regardless of the device/browser. I thought it was due to the system being unable to display a key authentication popup, but for the private account it worked (before I removed the keys).