A couple of things. First, the grouping order is important. The room you group others to is the group master. So, add the other rooms to your home theatre room; don’t add it to others. Also make sure you don’t have Ungroup on Autoplay set if you are using tv Autoplay. 

Hi,

In my setup once the home theatre is playing audio from the tv I try to add a secondary room (the kitchen symfonisk for example), but it can’t play ant sound even if the app is showing the audio animation and I can change the volume level. 
This happen if “Ungroup on autoplay” is set or if I disable it. 
What I’m missing?

thanks

That might suggest a version mismatch between the speakers, it’s hard to tell from your descriptions. I’d certainly check in your controller for updates to your speakers, and the Sonos controller itself. 

It also could be WiFi (or LAN) interference between the speakers and the router, perhaps, if both speakers are working with a normal stream, just enough to impede the amount of bandwidth required for a line in (the TV) input. I’d double check for any sources of potential wifi interference .

Ultimately, I would recommend that you submit a system diagnostic within 10 minutes of experiencing this problem, and call Sonos Support to discuss it. Don’t post the resulting diagnostic number here, they get sensitive about GDPR.

There may be information included in the diagnostic that will help Sonos pinpoint the issue and help you find a solution.

When you speak directly to the Support staff, they have tools at their disposal that will allow them to give you advice specific to your network and Sonos system.