Can you clarify what you’re trying to do?    From what I understand, you created a saved group in the Sonos app, call it “Downstairs”, and now you’re trying to use a GA voice command to play music on “downstairs”?

I don’t use Google voice much anymore, but this doesn’t exactly work that way with Alexa.  Alexa doesn’t recognize the speaker groups you’ve created in Sonos either.  Instead, Amazon has you create an Alexa group with the speakers as part of that group.  Then a request to play music to the Alexa group will work.  I took a look at Google support, and they do appear to have similar functionality...but it’s unclear if their groups can be created with Sonos speakers.  You probably know better than I on that regard.

As a general rule though, and voice command made,  whether Google or Amazon, is sent to Google or Amazon cloud servers.  It’s processed there before it’s sent back down to Sonos.  So if Google/Amazon doesn’t understand the request, it will stop right there.  It’s not a matter of sending a command to Sonos  for your speakers to figure out what to do with it.

From what I understand, you created a saved group in the Sonos app, call it “Downstairs”, and now you’re trying to use a GA voice command to play music on “downstairs”?

​​​​​​Yes! That's exactly what I want, but it doesn't work. 

You can create speaker groups with the GA, but only with Google cast devices. You can't mix it with Sonos speakers, or creating a Sonos group with that. And that's a problem! I understand why Google has absolutely no interest in adding this feature, but Sonos could simply add a work around. 

As described, Sonos could fake a Sonos device "Downstairs" that is basically a Sonos group and sync it to GA. So in GA it would displayed as a new single device. Voice control for singe devices are supported in GA. So it should work if I say "play music on Downstairs", the GA triggers the "Downstairs" device and Sonos knows that this is a speaker group.

It would be the same behaviour like Philips Hue ambient light settings. They are also synced to th GA and are configured in the hue app.

Synching Sonos with Google devices is not possible.  They use two very different methods of synchronization, and each method is intellectual property. 

Synching Sonos with Google devices is not possible. They use two very different methods of synchronization, and each method is intellectual property. 

This is correct, but this is absolutely not what I described and what I want. 

You have to be aware of the difference between the Google Assistant (GA) and Google devices. I want to simply control a Sonos group with my voice. 

Just off the top of my head, this would work for initiating playback to a group of Sonos speakers, but maybe don’t work so well for other commands.  For example, if you have the rooms that makeup downstairs is currently playing multiple streams,  what should be the response when you ask “what’s currently playing”?  How should volume change be handled?  I realize this  is handled with Google speakers, but Google is handling it, not Sonos.  Likewise, with Sonos speakers in an Amazon Alexa group, Alexa handles it.  Maybe it’s not an big concern, maybe it is.  Not sure.

It also sort of opens a can of worms since Sonos has an open API, if named groups are accessible to Google, then it would be requested to be accessible in the API.  But maybe Sonos is already working on this, as a part of their own voice assistant. Not sure.

As a comparison to hue, lighting and speakers are a bit different object types.  So some functions would obviously be different.  As well, hue requires a hub (last time I checked) that is there to handle this processing.  Sonos does not. Not saying it’s not possible, just that I wouldn’t really say it’s a simple thing to do.

Google Assistant does not work with Sonos groups as far as I know. Whether this is Sonos' doing or Google's I do not know. .

This is exactly what I want to do, and when the Somos One was advertised with Google Assistant support I assumed it could do what a Google Home device can do. I had to order the thing, have it arrive and then not be able to make it work, which is frustrating.

I’m trying to decide whether to return it, or just switch my system to all Sonos.  Sonos sounds better, but it’s a bunch more expensive. I was hoping to integrate the two. 

The same thing happens to me as to you, I bought a Move for the garden, my first Sonos speaker, and since I saw that it was compatible with Google Assistant, I assumed that it could be put into Google Home groups with the rest of the speakers that I have of different marks. Well, no, you can't do something as simple as that. I suppose Sonos will be interested in enabling it for whatever reason, not because it is not compatible, but because Sonos does not want to do it, for whatever interests. I had planned to buy the Arc sound bar and more, to put the whole house with Sonos, but seeing what I have seen, no more Sonos. And I did not return the Move, besides that it sounds great, because it is for the garden and well, it can be independent from the rest of the house, but a great disappointment for me Sonos, simply because something so simple, they don’t want to do it.

Google Assistant cannot possibly work work with a so-called 'saved group' in Sonos because there is no such thing really.  The saved group is really just a routine that executes when selected in 'on the fly grouping.  All it does is saves you having to remember which rooms are in the group and having to manually tap them all.

There is simply no programming object for GA to work with.  I don't think this will ever happen. 

I am not talking about the Sonos application, I am talking about Google Home, in which the Sonos Move appears and you can edit the room and the name, but you cannot add it to any group in the house along with the rest of home speakers, Bose does. And that isn’t because it can’t be done, or incompatibilities, it is because Sonos, for whatever reason, they aren’t interested in doing it

But that is not what this thread is about, so I don’t regard your comments as relevant.  You are just confusing the matter.  I was commenting on the question posed in the original post, not your off-topic contribution.

@Mariogd - Quote from Google website:

You can create groups of speakers, Smart Displays, and Smart Clocks so all of your devices play the same audio throughout your house.

This feature doesn't work on Bose or Sonos speakers that have the Google Assistant..

Link for this quote:

https://support.google.com/assistant/answer/9210727?hl=en#:~:text=You%20can%20create%20groups%20of,that%20have%20the%20Google%20Assistant.

I’d just note that a comment such as 

would only be valid if the author was entirely familiar with the Sonos code, and fully understood the commercial arguments.