The Media bay in Cubase 12 shows empty

I am on Windows 11 with Cubase 12 Pro. When I open the media bay on the right site I can see all icons (libraries). If I click on whichever, the content blinks up for a half second and then it becomes empty. Then if I can click on whichever icon it still shows empty.
I read the rescan the disk or “Quick rescan disk” could help, but I have no idea where to find this option (probably dummy user :-).
I would like use some samples but can not get it work. On my second PC with Cubase 11 Elements (Win10) I had the same issue, deleted the mediabay3.db, opened the Media bay and it started to work. Not with Cubase 12.
Could you help me anybody, please, how to “rescan the disk” and how to get it work?
Thanks a lot!

Open the full size MediaBay (default key is F9)

Hi, in the meantime I did the rescan (rescan in the Widows, still don’t know how to rescan a folder) - no success, restarted the PC, rescanned, restarted, rescanned and now suddenly it started to work - weird!