I found this nugget of news and perhaps relevant to my issue:
Link
Search Box Stuck or Not Responding in File Explorer
Here is a bug that is happening in Windows v1909 because of the new implementation. The problem with it is that it’s just that cursor is not blinking when you click on the box. Otherwise, it’s working just fine.
Type something and hit Enter to start the search
Now go back using the back button
Then click on File Explorer, and it will not display a blinking cursor, which gives you a feeling that it is not responding.
However, as soon as you press the down key/up key or type anything, it will start working again.
So if that’s what is happening with you, then it’s just the missing cursor, which should be fixed through a minor update.