My screen saver stopped working over a month ago. I tried all the fixes, except reloading Win11.
Reading through all the posts, I noticed one mentioned a USB game controller. I checked mine and found I had left my Realflight Interlink Controller plugged in.
Removed this, and screen saver worked again.
Although some posts mention they did not have usb game controllers, perhaps it could be that Win11 thinks they do, and then assuming they are playing a game, does not interrupt with a screen saver.
Even if my proposition is correct, I would not wish to advise on a possible fix.
In the meantime, thanks for the posts, a careful read and it got me to the root cause on my pc. Thanks, good luck, and seasons greetings to you all.