Aha! I had Sheet Protection for objects set on one and not the other.

--
David

David wrote

I have two workbooks identical in every way but with different names.
I have data validation set up identically in both
When I click one of those cells in one, I get a hand pointer that will
open the list. Not so in the other. I've examined all Tools|Options,
row heights and column widths, etc. between the two and see no
difference in settings.

Can anyone explain?