Home app : scene cannot be invoked with Siri “Sorry, I can’t find that in the living room”

I’ve added a few scenes to the Home app. Some, like exterior lights, can be invoked via Siri (“Siri, backyard lights on”). The scene name is “Backyard lights on” since you can’t add “on” or “off” to a Siri scene command.

But I have one scene, “TV Time”, that turns off the ceiling lights in the living room and sets the lamps in the living room to 25%. This works fine if I tap that scene, but via Siri I get “Sorry, I couldn’t find that in the living room in home.” Even if I’m sitting in the living room and it’s the living room HomePod that’s responding.