Ring Doorbell Pro setup light doesn’t spin

Ring Doorbell Pro will not go into setup mode. New installation, followed all of the directions, got to the point where it asks if the light ring is spinning, but it doesn’t happen. In fact, the ring is half lit, and then the final 3/4 of the ring just feebly blinks on and off. Tried uninstalling everything, reinstalling it again, same results. It’s connected to an existing mechanical doorbell, which functions fine. But connecting to the network ain’t happening. Run out of ideas. I tried uploading a short video to show what it’s doing, but Ring won’t let me upload a .mov file. So look at the two still photos and just click back and forth between them and you’ll get the gist of it.