1909, I have the same problem, File Explorer search stops working after a few searches.
I cannot access it to type, just hover the mouse over it, but my history of searches (e.g. *.exe) does not appear and the box itself is not an editable field anymore.
The fix is to go to task manager, kill Explorer.exe and restart it.
I've been using WIndows since Windows 3.0 in 1991 and I NEVER EVER saw such a Priority 1 bug (I was SW System Tester for many years in Siemens) being shipped out this way, and not being corrected after weeks of worldwide reports (just google...or bing it!)
Absolutely disgraceful.