I just spoke with telephone support at Ring. She had me download the Rapid Ring app but that did not work either. Then she told me that the firmware for my Stick Up Cam needs to be updated, and that update is being pushed out over the next few days. I am supposed to wait until Monday 1/27/2020 to try turning on motion recording again. In the meantime she suggests that I use the Rapid Ring app rather than the Ring app. So I suspect the problem is actually in the Ring app (as I alleged) and I will have to wait for that to be updated on my iPhone.
I’ll wait until Monday and try again, unless I see the Ring app updated on my phone before then.