I've been using Visual Studio for a very long time, and this problem has popped up multiple times for me with various versions. It's very aggravating, and seems specific to VS (other running apps work fine). It's happened with different machines, different Windows versions, different keyboards. It's very specific to VS. I'm currently running 2022 Pro V.17.14.0 Preview 2.0. And yep, it just happened.
In this case, today, it was right after I clicked off an install reminder for NVIDIA Nsight. Right after I clicked the "Yes, remind me again" option in the message box, my backspace, enter, and navigation arrows went dead. But my experience is that various things can cause this.
How I fixed it... I clicked the Find edit box in the Find and Replace window. Typed a couple of characters in the Find edit box, backspaced to delete them (hey, backspace works), clicked back on my Edit window and... backspace, enter, etc. are all working again!
I obviously can't speak for everyone, but the problem seems specific to the Edit window in VS. Click on another window, like Find and Replace, and it seems to fix the problem. A similar thing often happens for me with the mouse pointer in the Edit window, getting stuck as a pointer instead of reverting back to an I-beam. Slide it over to another window, like Find and Replace, and it starts working properly again.
So before you restart VS, or reinstall, just try typing something quick in Find and Replace, and see if that fixes the issue. Hope this helps!