Screen recording error / Screenshot app and QuickTime Player

I've been using the Screenshot app (cmd+shift+5) for hundreds of recordings.

Usually, when I press record, the Stop button appears in the menu bar. Today this stopped working: when I press record, the recording app just silently disappears without recording anything.

Reading your support pages, I tried to do the equivalent using "New Screen Recording" from the QuickTime Player menu bar. The outcome is exactly the same: at the time of pressing Record the recording tool disappears. The only difference is that using QuickTime Player, an error message shows, and the app itself stays running.

My MacOS is up-to-date, and so are all the apps I am using.

As a third method, I installed iMovie (today's version) as also from there one can launch screen recordings.

I can open iMovie and use it, but when I try to touch the camera setting, I get the error message "iMovie can't be opened"

Summary: all these apps that usually are able to record my screen, now fail.

The only unusual action today was that I updated a couple of Adobe apps. I can't see a logical connection between that update and the MacOS error.