Ctrl-Shift-L does not work for one particular website

With one of my websites BitWarden fails to fill the username and password fields when I use the hotkey Ctrl-Shift-L. Clicking the item in the BW browser extension, or using the right click context menu works just fine.

With this particular educational website (https://getalenruimte.online.noordhoff.nl/Login), the login fields are presented in some sort of overlay box and I suspect that the actual access validation process is ‘outsourced’ to an external server at a completely different url.

The two different urls are already included in this BW-item.
What more can I do to make Ctrl-Shift-L work?