Try unplugging all your speakers from power for a couple of minutes and reboot your router and phone. If this doesn’t fix it, consider wiring one speaker (not a Sub or surround speaker) directly to your router with an ethernet cable.

How are you attempting to group the speakers…

1 via the app

or

2 by pressing play/pause

@AjTrek1 I do it through the app.

@GuitarSuperstar Tried the ethernet cable solution, but it didn’t work. I’m actually the Office Manager for a start-up and we sit at WeWork, so we don’t really have access to reboot the system.

We do have our private network and IP within the WeWork-network, so that should not be the problem.

Hi @Hedvig

Welcome to the Sonos Community!
In this case, I believe the issue you experience is due to the fact that Sonos devices expect to be able to communicate with each other directly, but utilising the same WiFi channel that your WiFi is on. However, two of the speakers are connecting to an alternate WIFI Access Point which is using channel 6 instead of 1.

Is it Dining Room and Small Lounge which were left out of the group? If so, then this is definitely the problem.

There are two ways to fix this:

1. Get your IT department to put the WiFi APs on the same channel as each other.
2. As @GuitarSuperstar suggested, connect any one Sonos device to the router with an ethernet cable, permanently. It sounds like you will also need to speak to your IT department for this to work - it depends on the configuration and security of the network.

I hope this helps.