Why do HomeKit automations fail after a power outage?
I've seen this question asked a good many times, but I've seen few answers.
I called Apple support and they walked me through many steps to get things working again.
Then (last night) my power failed again due to a storm. I tried this, and it worked:
1) Unplug the modem, the router, and AppleTV. Wait a bit.
2) Plug in the modem, and wait until it's up and running, then plug in the router (and wait til it's running) then plug in the AppleTV.
It worked! My automations came back on line!
Maybe it'll work for you too?