These are the settings (I believe) you should have for the Aruba router, that’s if you perhaps just want to double-check those to make sure things haven’t changed during an update etc:

• Log in to the router
• Go to Firewall Settings → Multicast
• Enable Multicast. (Uncheck "Require IGMP Membership reports for multicast data forwarding" and choose "Enable reception of all multicast addresses" in Multicast Policies.)  Click "Accept".
• Go to Network.
• Click the Configure button for the LAN zone (default name ??) Click the Advanced tab and check "Enable Multicast Support". Click OK. Click the Configure button for the WLAN zone (default name ??) Click the Advanced tab and check "Enable Multicast Support". Click OK. Click "Accept".
• This should automatically modify the Zone-to-Zone rules to "Allow" the traffic for IGMP for the LAN and WLAN zones (under Firewall).

The above was taken a while back from a previous Staff posting, so my thoughts were it may perhaps assist.

Hello! Thank you for the answer! But I have Aruba Access Points not Router. My models do not have this settings ... :(

Ah I see - and is the Router’s own in-built WiFi adapters enabled or disabled?

Happy new year! :)

Yes, the router's WiFi is disabled. I only use the Aruba WiFi.

Are the Aruba AP’s able to be set to use the same fixed WiFi channel? - If, so, I’m wondering if that might fix your issue by setting them to each use either channel 1, 6 or 11.

…and also Happy New Year too.

The Aruba APs choose the best channel. That's channel 1 or 6. It's not a good idea to set the same channel for multiple access points.

The Roam connects to 5 GHz btw. :)

I think you might be surprised, if you were to set/fix the same channel on the AP’s, to say channel-1, rather than allowing them to auto-select and move the Roam to the 2.4Ghz band (ensuring the 5Ghz WiFi credentials are removed from the Sonos App’s network settings, that’s assuming the AP’s have different SSID’s for each band), I believe you would see an improvement. You can always maybe try it temporarily to see if works.. but just give things a while (20-30 minutes) to settle after making the changes. 

If it doesn’t work, then simply revert back to your current settings.

Thanks! I tested your idea with a completely new wifi network, but the problem persists.

I am able to connect to the Roam with it's IP. The Roam has definitely a connection to the wifi but the Sonos app is unable to see it.

I will return the Roam. It's really annoying that the Roam doesn't use the Sonosnet ... It's so complicated ...

It’s not really plausible for any of the Sonos ‘portable’ products (Move/Roam) to use a SonosNet mesh signal, because the mesh signal would likely be jumping all over the place between Sonos devices as the Roam/Move was carried about the home - breaking and (re)creating connections wouldn’t be too helpful to any setup. Mesh systems have disadvantages aswell as advantages.

Putting all on the same WiFi channel/channel-width usually helps things however.

Finally! I have found the (simple) solution to the problem!

1. disable broadcast filtering (if you have NO rear speakers for surround sound, ARP filtering is also possible)

2. uncheck all "Services" (Bonjour, DLNA ...) 

3. uncheck all Airgroup Services (AirPlay, Airprint etc)

Adding services is NOT necessary and causes problems with speaker detection. Disabling broadcast filtering is sufficient!

Screenshots will follow! 

Screenshots