Air Tag Registration Fails

My first instinct was to sign out of iCloud and sign back in. Bad move. That would disable or delete things. Then I realized the phone has to register (similar to signing in) with iCloud every time it turns on. So I cycled the power. Solved

That does not address the issue that the tag and/or iCloud somehow thought I wasn't signed in.

Yep. Been there, done that. Followed Apple instructions to the T. Matter of fact, that page is still open in another tab of my browser. No change in response.