Apple Watch will not activate: Pair→Update→Pair→Update→etc

iPhone 7+ updated to 13.4.1 this morning.

Refurb Apple Watch 3 delivered this afternoon. Pairing always says "must update to latest Watch OS to finish pairing. Tap update, says "may take a few minutes" but in less than a minute, it is says "unpairing" and than asks me again to pair it. If I tap "skip update and continue," it asks which wrist, says "connecting," and then "unpairing" and I'm back to where I started.

Where do I wave the dead chicken?

Solution 1:

Watch refused to turn off for the purpose of reboot. But doing a hard reboot of both iPhone and Watch changed the behavior. There were still some things that shouldn't have happened, but eventually I got past them all.