We've recently become aware of an issue with grouping multiple speakers for a small percentage of users in our updated Sonos integration. While we believe that this experience generally works for most users, we've seen reports of issues with surround groups when used with Yonomi. We are currently working to diagnose and fix this issue and have outlined a couple of options that may help in the interim.
In Yonomi, create a Routine and set all your speakers to play the same Favorite/Playlist. This should group all the speakers and play the same music. Instead, it groups all the speakers except the one set up as surround sound.
1. Break up surround sound on Sonos, use vanilla grouping for the time being in Yonomi -- create a Routine and set all your speakers to play the same Favorite/Playlist.
2. Remove and re-connect your Sonos Cloud Account in Yonomi