Is CEC enabled on your TV and Chromecast?

Yes it is, and it works if if issue the command from the Google Assistant app on my phone.

So did you rename the "Sonos (Room Name) TV" device, or did you assign it a nickname instead?.. I would perhaps try assigning it a unique nickname instead of renaming the device …and see if that works for you, but remember to include the nickname in the voice instruction and ensure no other device/room in the Google Home has the same name.

Just as an example, if you assign the control a nickname of "BST’s TV” then it’s ‘Hey Google turn on BST’s TV"

I have exactly the same issue. Google assistance can turn on/off my TV but when asking Sonos to do it, I receive an unknown error. However, I can still stream audio and video via Sonos. It is only the turn on/off function, which is not working.

It have been working for years up to now. I did not change anything, the problem just suddenly appeared. I have the feeling it was shortly after updating my Sonos.

Hey Ken

Thanks for your reply, I am not sure I understand what you mean. My chromecast is not known in my Sonos app/environment. I tried renaming the Chromecast device in the Google Home app, here I tried renaming it to something unique.

And if I do “Hey Google, turn the volume up on BST’s TV”, than that command works. This is what puzzles me greatly, some commands work, but turn on/off does not.

Sometimes more than one device can control the on/off functions of a TV and be linked to the voice assistant.

As an example my LG TV has the Google assistant built-in and the TV skill/action itself can turn on/off the TV (mic is built into the TV remote), I can also control the TV with the Sonos action/skill (in works with Google) and also with the Harmony action/skill linked to the Harmony Hub that I use to change TV channels - so in each case, I have called the TV by different names for each of the devices - my Sonos nickname is ‘Living Room TV’, whereas my Harmony Hub knows it as just ‘TV’ and my LG TV calls it the ‘Lounge TV’ - so depending on the name I include in the voice instruction will relate to which action/skill actually switches the TV ‘on’ or ‘off’ etc... and most such actions/skills default their own connected television names to ‘TV’ - So that’s why my suggestion is to look at which devices might be controlling your TV (i.e. Chromecast & Sonos etc.) and change their nickname to something ‘unique’ and include that in the voice instruction and see if it solves your issue.

Ah, got it. My TV has no built-in functionality for this, and I have no other smart gadgets that can control my TV. Only the Chromecast via Google Assistant :)

Ah I see, I thought it was a Sonos-skill/action related question and you were perhaps trying to use the Sonos TV control (action/skill) that comes with a Sonos HT product connected to the TV. Sorry that’s my mistake. I will crawl back into my hole. It might be worth giving the router/network a reboot to see if that fixes it perhaps?

I already tried that, but again - I can use voice commands to control volume on the Chromecast. And I can use the Google assistant app on my phone to turn the TV on/off, so I do not think it is related to connectivity :)

just got to jump on and bump this.

exact same issue. I have a Chromecast connected to my tv which is also connected to my Sonos beam (via ARC). if I use any other assistant enabled device I can turn the tv off but when asking assistant on the beam it responds with 'something went wrong for xyz'. 

I've tried removing and re-adding these devices to Google home, using custom names etc. but it seems like it's a Sonos assistant issue not being able to successfully send this one command to the chromecast.

can also verify that other commands such as adjusting the volume, work. 

it also might be that it's trying to intercept and run the turn off/on command with the tv control that comes with the beam? not really sure

Exactly same error and issue.. suddently stopped working around the same time of your post.

It tells an unknown error and even names my chromecast, even if I just say “Turn on the tv”.

Very weird. Using danish as language. Never had an issue, and all other commands work fine.

@TNE26 & @periodic_purge,

What does your Home Screen show in the Google Home App? - can you perhaps post a screenshot of the two entries for the Sonos HT product and if not done already, reauthorise the Sonos Action/Skill too.

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EXACTLY THE SAME ISSUE!!

At exactly the same time! 
 

Unable to resolve, is there a way to get advice from Sonos on this?!

You should be able chat to Sonos Support Staff via this LINK.

Exact same issue here;

I have a ‘old’ stupid TV with a Chromecast connected to it.  For the past years I was able to say: ‘Hey Google, turn on the Kitchen Television’, but now since a few weeks that doesn’t work anymore.

Saying: ‘Hey google, Pause kitchen television’ still works! (When it plays Netflix or anything)

When I open the Google Assistant App on my iPhone and say ‘Hey google, turn on Kitchen Television’ it works!!

I also tested with a Chromecast TV and Chromecast Ultra, works!!  So only the old Chromecast is not working with Sonos!

I am on Sonos v14.18   Anyone able to test with an older version?

Same issue here. Any luck?

I have the same issue. Everything works until I say “turn off ftv name]” then google assistant says an unknown error occurs. 

Exact same issue. We could still turn off by saying “Turn off chromecast” or “Turn on chromecast” but saying “Living room TV” it would throw an error. After factory resetting the chromecast to try and fix the issue, it is now completely broken and saying “Turn off chromecast” also doesn’t work anymore.

Same issue here. Can't use the Chromecast to turn the TV on or off through a voice command issued to the Google Assistant on Sonos One anymore. Used to work fine, but stopped all of a sudden.

Maybe see if the suggestions in this Google support link may assist you to fix it:

https://support.google.com/chromecast/answer/7498991?hl=en

Unfortunately not. I can control TV power using Google Assistant from any other device, just not my Sonos One. Used to work, but stopped within the past month. Tried removing and relinking Sonos to Google Home again, but to no avail.

I agree with “jtwall” – if I type “Turn off TV” in the Google Home app it turns off the TV just fine. Only Sonos products has issues turning off the TV. We have 9 different Sonos products with Google Assistant. It is the same with all of them. Has there been any feedback or commitment from Sonos at all?

I’ve not seen anything, but you can perhaps chat with Sonos Support Staff via this Link about the TV control issue, that’s if you are unable to resolve it. I’m beginning to wonder if Google may have withdrawn the feature from 3rd-Party devices, like Sonos. It would be nice to know if anyone currently has this working?

Same problem here! First I thought it was a ghost Chromecast or TV that it tried to control, but it actually seems to be the Chromecast Ultra. Don’t have the problem with Google Home Mini or GA on the phone.

It’s also interesting to know if it’s only an issue with Chromecast Ultra. Can anyone confirm with the older regular HD Chromecast or perhaps the latest Google TV?