It depends what you’re trying to achieve, but it sounds like your issue lies with Alexa ‘enabled’ groups where the echo/Alexa components control the Sonos grouping/ungrouping features. Perhaps start by removing your groups in the Amazon Alexa App and setting them up as required. 
 

The screenshot attached shows an example Alexa ‘enabled’ group…

In summary, the controlling Alexa/echo devices in the first section of a group will auto-group the Sonos speakers mentioned in the third section of the same group for music playback when speaking a playback instruction to the controlling echo device.

So I suspect this might be where your issue lies in the Amazon Alexa App.

Here are some further useful links on Sonos and Amazon Alexa Groups:

• https://support.sonos.com/s/article/3169
• https://www.amazon.com/gp/help/customer/display.html?nodeId=201749250

Hi Ken. 
I cannot read the screenshot on my phone, but will look tomorrow on the computer. 
Ahead of that, I don’t have any groups either in Alexa or Sonos. 
All I want to be able to do is be in the office and ask Alexa to play through those speakers. The ones she cannot find. 
Thanks for the prompt reply 

Regards 

Are all the speakers showing in your Amazon Alexa App device list? If not, you may need to install/reinstall the Sonos Skill and let Alexa scan to discover those devices… you can then use Alexa groups (or not) to play your default streaming music to your Sonos devices.

Hi Ken

Every speaker appears in the Alexa app, except this pair. I have deleted, re- installed, taken the speakers off the wall and re-sited them just in case the SONOSNET was having travel, but to no avail. They are invisible to Alexa, but not to Sonos. 
Regards 

Just to clarify too, all your 9 speakers show in your Sonos App together …and in the ‘about box’ listing all are in Wireless Mode WM:0, so presumably you just have the one Sonos device wired to the main router. Can you ensure the following is in place too:

• The one wired Sonos device is set at least one metre away from your router.
• The SonosNet Channel in the App is set at least 5 channels away from your routers 2.4Ghz channel.
• If you do not have any Sonos portable devices (Move/Roam), that your WiFi credentials are not listed in your Sonos App ‘Settings/System/Network/Manage Networks’. 

Note because you have already stereo paired the speakers in the Sonos App, they will only show as one device/room in your Alexa App.. if you have any other ‘smart’ devices make sure they don’t have the same name as your speakers too.. as an example you wouldn’t want a smart-plug called ‘Office’ and a Sonos Room called ‘Office’ aswell as that may cause Alexa some confusion. So best to have them uniquely named.

It’s often worth removing and re-linking the Sonos ‘skill’ in the Alexa App as that can sometimes show two separate ‘systems’ if the device(s) were originally setup on different Sonos Households, or it might just find the missing room and resolve your issue.

Also take note, that when you remove/reinstall the Sonos Skill, if you see a screen ‘similar’ to the image attached, where it invites you to select a Sonos system as that might prove to be useful information here too.

Hi Ken

Now on the big system . Still cannot see your screen shot.

To clarify,

All of the Sonos system is connected to the Boost and the Boost is directly connected to the router.

The Sonosnet gives me three options for the channel. 1,6, & 11. I have tried all the combinations and none of these work.

I have no portable Sonos devices.I have two arcs, a beam, a sub, two one SL’s, 3 Sympfonisk and a boost.

The wifi system is 5G, but I am running the Sonosnet on 2.4ghz and have turned the 5G off to ensure this.

The Alexa discovery will just not find these speakers. I have had them as a sterio pair and then seperated them out. Still nothing.

As I said, Sonos sees them all and reports all on WM0.

Last night, as an experiment, I fired up the kitchen arc and coupled the office to it. The speakers worked, which was an assurance at least. I could hear Spotify played on all three speakers. Finished for the day, i disconnected the office from the arc and shut down. This morning I asked Alexa to play kitchen and it was quiet. In the distance i could hear music. Now the office speakers were playing through the kitchen instruction. I had to go into the app and disconnect office again and then and only then could I get kitchen back.

I do have many items connected to Alexa that are all home automation items, and these all work perfectly well, provided i pay attnetion to what i ask her but that is always user error.

I am perplexed to say the least.

I am going to remove and reset the skill in Alexa and see what happens.

I would switch on your 5Ghz WiFi on your router, the Boost (SonosNet) network is entirely separate to your WiFi signal - make sure you have removed the WiFi credentials in the Sonos App network settings. Also ensure your smart home devices in the Alexa App are all uniquely named. Removing and reinstalling the Sonos Skill after doing those things first, is the probably the best way to move forward when trying to resolve the issue (especially removing any stored WiFi settings in the Sonos App first).

Good morning Ken

Finally cracked it.

Followed the advice of deleting the skills tab and re-instating the skill. Discovery scan.Nothing !!

Changed office to My Office and re-scanned. Nothing.

Changed My office back to Office, Discovery scan and Bingo. Everthing appeared.

I don’t understand why, but at least it all works now.

Thanks for all your help and advice

Appreciated