I’d call Sonos Support, they can see internal data hidden from us users.

There were a number of folks in the history that were complaining, the thread seem to have stopped. I was hoping there was a fix which I missed.

I also noticed that there was an update in September, which unfortunately did not seem to fix it.

Unless is see a good response, I’ll give support when ai get a chance.

Update, my system starts all the time with the soundbar/amp for rear speakers in the living room, then attach the others or dining room then to the soundbar. It would always fail when the grouping includes the living room. I tried just now grouping with other amps without the living room, so far it connects.

sound like a connection with my soundbar and surround amp is causing a problem. Connection direct with only the living room soundbar and surround amp works.

Hmmm.

Oh, I got it to work much better. Turned out the Soundbar was not updated. I had to select it manually and update it. Auto update or even notification does not work.

Now is found if I put too much amp/speakers I’m a group, about 5, all speakers drops out. I could live with that limitation. I have to report this bug to Sonos.

A diagnostic and call to support can see the internal data and give you an idea of what is happening.

Trying the interference FAQ might get you there without the call.

https://support.sonos.com/en-us/article/improve-your-sonos-products-wifi-connection

https://support.sonos.com/en-us/article/reduce-wireless-interference

Thanks, except for one Connect, all the A mps and Soundbar has wired Ethernet and capable of wireless. Tried both.

Every once in a while, it still occurs. Just happened couple of weeks ago.

Again it a problem with one or more devices needing firmware updates. The devices are not automatically updating and launching the app does not force or notify me that the device needs updating. 
 

My latest find is, if I go through the motion to add a subwoofer, it will say it can until firmware is updated, an then allows me to update it. Once I do it for each device it would work again. 
 

Next time I will try looking at the firmware version using about.

How odd, do you have static/reserved IP addresses set for your Sonos?

That has helped some folks in the past that had odd issues. Your router's DHCP page should tell you how to do that.

No static/reserved. The app does communicate to the units individually,

The problem is when I group the amps together to play the same music and it does not work when the units are at different firmware levels. I don’t group them together all the time, it is nice when playing music group for background. Filling the house with same music like during the holiday with guests,  does not need to be as loud for the individual speakers when you do this.

if it fails again when they are at the same firmware level, it will try that.

thanks