I bought my 55" Sony Bravia x930e at the beginning of this week and love it. I am pretty interwined in Google's "Ecosystem" with 4 Google Homes, a Pixel phone, a chromecast on another tv, etc. so the appeal for an AndroidTV was there. For the first several days I was able to turn on/off the TV using Google Assistant (either with a Google Home or my phone) flawlessly and it worked beautifully! But this morning I had to unlink/relink the Bravia from my Home account for unrelated troubleshooting reasons and now I can not turn the tv on/off remotely with Google Assistant anymore. When I give the command Google acknowledges it but does nothing. But strangely enough if I tell the the assistant to play something when it is off it will turn on and play said thing. I am trying to figure out how to get this feature back. I made sure the tv was up to date and that Bravia Sync (which I believe to be the HDMI-CEC toggle) is on. Any ideas??
Sorry I'm typing this at work so I cannot provide the exact instructions but I believe I have the solution. In settings menu on the TV about allowing other devices controlling it. You have to turn it off to deregister the TV and then turn it back on again. I would recommend to remove it from the home app again before trying this again. If I also remember correctly this may add a copy of your TV in the home app.