Not a fix and not for all cases, but just as a note. I’m using Sonos speaker to read all kind of notifications from Homey. Sometimes to play an mp3 file. I wrote a simple Python script, which is playing to the speaker via local network. It exposes HTTP calls interface to play or speak a text. For such limited cases it does not depend on Sonos or Homey clouds. It depends, though, on Google text to speech to generate mp3 from a text requested. Running on RPi. Perhaps the same can be done with JS in a Homey application.
People often complain way too easy. Let me also share something positive: after the service was up and running again, the issue for my case was solved.
Unfortunately the issue is back in my case. Restarting the app doesn’t solve it.
Checked the status (Sonos Status) and all systems are operational…
But there wasn’t a Sonos App update, jus a HP23 firmware update (v12.4.0) on Monday.
Have you already tried to Repair the speakers? Or restarted Homey?
Have you made any other changes?
Have you maybe updated your WiFi router? After updating my Wi-Fi router and/or my AccessPoints, sometimes I have to restart them after the update to fix the problems with Homey, even though my Sonos speakers work with the Sonos smartphone app and Apple Music without any problems.
Went for a run and now I am back, it is working again 
Still having problems with Sonos, on my roam speaker, i can change the volume but when I try to start or stop a play list i got the error “The selected group or device is currently not available, please check the connection or try to repair the device” I have tried to repair and restart the Sonos app but no success. The speaker is online and accessible via the Sonos app…
Try to update the Sonos firmware (speaker firmware), auto update does not work always
All Sonos device are on the same version and there is no update available but the roam is still giving the error
Roam:
Sonos OS: S2
Version: 17.0 (build 85.0-64200)
Hardware Version: 1.33.1.8-2.9
I have restarted the homey, restarted the Sonos app, did may repairs but the result is still the same
