Adding an Apple TV to the Home app in tvOS 11.4 tvOS updated yesterday to 11.4 on my Apple TVs, and on startup asked what room each Apple TVs is in. However, it didn't show the list of rooms I have defined in my Home app. It showed a generic list of room names. I selected one, expecting that I could access it and change its name in the Home app, but now the Apple TV is in limbo somewhere and not accessible to the Home app. And there doesn't appear to be any user interface in tvOS to bring that room selection back up.

How can I regain control of my Apple TVs in the Home app?

Addendum: here's a pattern (perhaps) that I hadn't noticed before: My Apple TV 4s did show the correct room list and allowed proper linking. The Apple TV 4Ks did not, and those are the subject of this post. They do show as Home Hubs in the iOS Home app, show up as Airplay destinations, and have all other indications that they should work.

Addendum #2: I factory reset one of the misbehaving Apple TV 4Ks and it allowed proper room selection. It also has a room selection menu in the Airplay settings. The misbehaving Apple TV 4K does not have that menu choice in Airplay to get to any Room settings, so I'll probably factory reset it too. I suspect a bug at this point, but it's not clear why it triggered for some Apple TVs but not others.

Addendum #3: Factory reset of the remaining unit corrected the problem. Why this happened to multiple 4K units and not to any Apple TV 4s is a mystery.
Was the Apple TV your home hub? If so then you can check and see if you see Homekit as Connected:

On your Apple TV, go to Settings > Accounts > iCloud and make sure that your Apple TV shows HomeKit as Connected. If you don’t see HomeKit, then your Apple TV isn't connected as a home hub.

Set up Apple TV as a home hub


On your iOS device or Mac, set up two-factor authentication for your
Apple ID. Then go to iCloud and make sure that you have iCloud
Keychain turned on.
On your Apple TV, go to Settings > Accounts and make sure that
you're signed in to iCloud with the same Apple ID as your iOS
device.
After you sign in to iCloud, your Apple TV automatically sets itself
up as a home hub. To check the status of your home hub, go to
Settings > Accounts > iCloud and look under HomeKit to see if your
home hub is connected. Learn what to do if you don’t see HomeKit.