My Hisense u6G with built in chrome cast can’t be controlled with by Nest or assistants throughout the house. The TV has l been successfully added to the “house” and I can use the in-app remote in the Google Home iOS app. But if I were to ask Google Assistant in the same app to turn the TV off/on it would give me an error.
Sorry for the issues you're seeing with Assistant commands. I imagine that's pretty frustrating. Can you tell me what the error says? Also, could you let me know what region (country) you are in? Also, is this a new issue, or has it never worked for you? I look forward to helping you work this out.
I understand what you're looking to do now. What you need to do is set your TV as the preferred playback device. The instructions for doing that can be found here: https://bit.ly/39dR97U.
If you have any issues getting your playback set up on the TV after using the guide, please let me know.
Thanks for the photo. Give these steps a try: