A few weeks ago I was able to turn on and off my Sony 900f with Cromecast built in via my Google Home. Recently I haven't been able to. I don't know what changed, but it was working great and over those few weeks I become very use to using it to power the TV. Why doesn't it work anymore? Am I missing something?
Try deleting your TV in the Home app and pair it again? Mine just worked when I told Google to turn off my “Sony TV”, which is what the TV is named.