I did, but it may not help many others.
There was the usual Roku says it's Prime, Prime says it's Roku. Every other channel except Prime was working, which argues for a Prime problem, but that might not necessarily be true.
I was connected to my WiFi box in the same room, but at some point had switched to Comcast cable service, and their modem (with Wifi) was also in the same room. Switching the WiFi connection to it solved the problem.
So apparently the Prime app is sensitive to something in the WiFi that isn't interfering with other apps.
