SSDP discovery (M-SEARCH) gets no response from any player – not even player-to-player

You need to contact Sonos support directly.

I have none of the issues you are posting about, and I have the latest app and system updates installed.

My recommendation to users who have prosumer/enterprise networks in their homes, is to leave their Sonos speakers on the same trusted VLAN as their phones.

I have a Ubiquiti network in my home with an IoT, Camera, Guest and Trusted VLANs configured for device segregation. I have all the firewall rules configured correctly, with Multicast enabled.

I still have my Sonos speakers on my trusted VLAN so that I can avoid connection issues that can sometimes happen after a firmware update to your network equipment.

While I do not use an Android phone (I do not believe this is isolated to Android), using a flat network with Sonos will avoid many of the connection issues users post about.

I am not aware of any networks being compromised because a Sonos speaker was hacked.

My speakers already sit on the same VLAN as my phones. That's my normal daily setup, not a segregated IoT VLAN. The IoT-VLAN test was a diagnostic experiment, routed through my firewall, meant to isolate the cause.

And the result contradicts "flat network avoids issues": discovery from the SAME VLAN as the speakers failed worst and most consistently. The routed cross-VLAN path stayed comparatively reliable, until it broke too (see point 3).

Point 3 kills the VLAN explanation entirely. I captured one Sonos speaker, freshly rebooted, searching for the other speakers in the same household. Same flat L2 segment, no routing, no VLAN boundary, no phone or app involved. The other players stayed silent. Players failing to answer other players sitting right next to them isn't a segmentation problem by any definition.

One question for you: which access points are you running? I want to rule out that my UniFi APs specifically drop or mishandle SSDP multicast, versus something in the Sonos firmware. Port-mirroring on both AP uplinks already showed the M-SEARCH packets leaving the switch correctly toward the APs, so I lean toward the players themselves, but a working setup on different hardware would confirm it.

One more data point worth adding: the timeline differs sharply between the two setups.

On the same VLAN as the speakers, the problem showed up within 1-3 days.

On the separated VLAN, routed through the firewall, the first devices stopped responding to control commands after about a week, and it took roughly two weeks before every speaker had disappeared entirely.

Same endpoint, same root cause, just a much longer runway before it hits.

No VLANs here but my Ubiquity AP has never had an issue with Sonos since I got the basic configuration right. I don't know where to begin with your issues but it is unlikely to be hardware related. 

I don’t have these problems using a UniFi AP. I also don’t use VLANs.

I would think that if the issues you are having were common, there would be thousands of irate sonos users posting here that their systems have suddenly stopped working. So it would seem to indicate the problem is with your specific network setup.

You haven’t really included any information about your specific network that would be useful in troubleshooting your problem.

Sonos support may be able to identify what’s happening with your system. Try submitting a diagnostic (Submit Diagnostics) within 10 minutes of getting an error. Then call Sonos Support (Sonos Support) to discuss it. They may be able to see what’s going on since they have access to information about your network and sonos system that no one here has. Don’t post the diagnostic number here.