Thanks for responding, Dave. I was a bit puzzled about your response cause on my computer File menu doesn't go to Exit, there is no red X box at the top right and I don't know what Task Manager is. Then I realized your advice may be for a PC. My bad - I'll remember to say I'm on a Mac next time.
It's always great to reach out and have another set of eyes helping out. As it happens, I had a software update to do, which calls for rebooting. That must have been it, because the search box is working again.
So I'm happy that you extended yourself to help, and that one of those things was cross-platform and seems to have done the trick!