Yesterday, two of my motion sensors got stuck on “motion detected”. I got one (not ST) to work by removing the battery and reinserting it. The ST 2015 one (like the one you have) needed me to remove it and rejoin it. Like you it never showed up in the pairing screen, however I later noticed that it has been added with just the name motion sensor. I renamed, re-added it to all my automations and it was good to go.
This morning I walked into my living room my lights didn’t come on. I walked into the kitchen and the lights didn’t come on. I went downstairs and the lights didn’t come on. At the bottom of the stairs I have a button controller that can turn on the lights, I pressed it an nothing happened. I have a door sensor on the closet, I opened the door and the lights didn’t come on.
Ok… so I told one of my Echoes, “Alexa, turn on the kitchen lights,” and bang the lights came on.
I looked into the device history on the devices and I noticed there were no events for any of my battery powered ZigBee devices after 4AM EST this morning. I don’t think that all of my different battery powered devices went bad over night. It’s more likely something they did at ST f’d everything up again. I tried pulling the battery to no avail.
Point being, don’t buy anything new just yet, your devices are probably fine. It’s possible the update on Monday will resolve the problem (although it could also make it worse.)