NOT to credit Google for doing anything to resolve this issue, but I
coincidentally upgraded to an iPhone 13 Mini, and was immediately able
to add the missing Nest Protect. I'm guessing it's a bug related to
memory. It now works for me.
@GarrettDS Please don't lock this thread. Seems inappropriate to shut it
down when we have no ETA for a solution, and presumably hundreds of
users with same issue. At least here Google/Nest can get some idea of
the number of us affected and frustrate...