SwansonPhotos – Thanks much for your help.
No site link yet because I pulled the code off and was working only on localhost (where the problem also showed up.)
But it’s apparently solved now. I started from scratch, created a new DB, reinstalled WordPress. The only difference this time is that I created the menu before I created the child theme instead of after. (Previously the child theme was activated when I created the menu.) Just commenting on the process — I doubt this is cause & effect.
It works and I have no idea why ??
Thanks again for your help.