Connecting Sonos to home app

I am trying to add my sonos installation to the home app. I have a surround system, and two separate speakers. I see all three icons appear in home but as soon as I want to connect I get either the message: AirPlay unable to connect to xxx (name of sonos I want to add). Or I get the message: Add accessory not possible. Make sure your iPhone is connected to a Wi-Fi network and try again.
I've already reset the router, uninstalled and reinstalled all apps. I have contacted sonos. They can't find any problem in my system. Is there anyone who can help me please?