If this is the case, chances are your PC has updates which need to be installed, at least from my experience. You need to use the start menu to get that sorted.
I just got a new laptop with windows 11. I had the same issue, and it turns out it was because I needed to update. (At least that is what I expearienced.)
When I want to shut down my computer or put it to sleep, I press Windows, X. The options for shutting down and signing out are towards the bottom of the menu.