This will likely be because there is something blocking the SSDP multicast ‘device discovery’ packets between the controller and your speakers - first check it’s not your mobile that’s the cause, or ‘other software’ (perhaps) running on the phone, such as VPN client, firewall, or antivirus. Having eliminated that, then look closer at the router settings to ensure it supports multicasting/discovery between all its LAN segments and switch off things like QoS, Airtime Fairness etc; to ensure they are not interfering with things.

If you have other wireless access points, besides the router itself, see what happens when you power them off and let all run on just the router AP only - if still no joy, then (if not using already) see if running on SonosNet makes any difference to device discovery, but note that portable Sonos products, such as Move, or Roam, do not support SonosNet, nor do the Sonos Era products, but it might help you to identify if the problem lies with the router.

For the router itself, disable any ‘guest’ WiFi network and set the routers 2.4Ghz band to use a non-overlapping WiFi channel - 1, 6, or 11 and set a channel-width of 20Mhz only - I also suggest having the WiFi band compatible to 802.11 b/g/n with a security mode of WPA2 AES.

Ensure that WiFi SSID is added/showing in the Sonos App network settings for all products and just remove the 5Ghz SSID for now.

It’s not entirely clear if you created a new Sonos Household and ‘split’ your system into multiple parts - you might need to clarify if you created a new Sonos Household with a reset App, or used the ‘Add Product’ option in ‘Settings/System’?

I would strongly recommend you do not keep factory resetting your speakers, it just wipes out all diagnostic information and gives Sonos Support Staff nothing to work with to help resolve your issue. A factory reset is best done on the advice of Sonos Staff, or occasionally on the advice of some experienced Sonos users and only ever do it as a very last resort.

I doubt that Sonos Staff would be able to assist if you had repeatedly factory reset your speakers - it likely wired out the diagnostic information needed to discover what was happening with your system.

I would try some of the things suggested around your mobile device and network/router setup to begin with, but  more detail is really needed as it sounds like you may have several Sonos Households with devices operating under different Household ID’s on the same LAN subnet - which, if that is the case, will definitely result in devices showing up and disappearing in your Sonos App.

 You might even be better off going back to Sonos Support and see again if the Staff there can perhaps at least check and get you back up and running with one system/household only and then afterwards go onto resolve your network ‘device discovery’ issues.

I hope the above begins to help you get your issues resolved,

Thank you. I appreciate the detailed response and valuable recommendations. I am not very technical but will attempt some of the areas you suggested to resolve. If anything it kindof reinforces I am a bit over my head and the simple system I was looking for is likely not Sonos. 

I will see where this leads me but I do appreciate your response which further confirms a product return will likely be in my near future. 

Much appreciated.

Yes, Sonos is a computerised multi-room wireless/wired network audio system and the players need to successfully communicate over the various LAN segments and speak with any controllers too. It works well if the network is setup correctly and robust, but if there are any networking issues, then it may require some network configuration, which I suspect is perhaps the case here. 

If you’re struggling to resolve these things yourself, the best option is to definitely go back and speak with Staff at Sonos Customer Support - they might even raise your case to a Level-2 engineer to get you back up and running, particularly if your happy to provide them with local network access, but just see what the Staff say.

I hope you can get things sorted.

Bizarre update. After 4 hours of trying to troubleshoot I restarted my phone (although I did this multiple times) and for some reason the pairing worked and the speakers are connected to the app again. I will still contact support as suggested but thought I would post as this type of strange technical phenomenon seems to happen often to me with the Sonos app. 

Too bad I wasted a Saturday doing it

And we're back :( 

Like clockwork similar to last weekend and many weekends before there is a Sonos product that either disappears or cant be discovered.

This time it is my Sonos Move2's which have disappeared from my products in the app. I didn't use them all week and they are fully charged. Unless there are some good ideas as to why this might happen that I can troubleshoot I am just going to re-add them again. Just want to document how this continously happens but certainly not wasting another Saturday like last week ;)

As a guess, it sounds like a network multicast discovery issue between your controller and Sonos products over your network - maybe see this link for an explanation and some things to try…

https://en.community.sonos.com/setting-up-sonos-228990/adding-new-sonos-to-app-6871856?postid=16603151#post16603151

Thank you Ken. Really appreciate the quick reply and guidance. Will follow the link and give this a try. 

Had recurrent connection problems with my Sonos app and Android 13 on Samsung S20+ and was stymied. Sonos help desk tried to help but problem persisted. For me, turns out it was my VPN (NordVPN).  The minute I turned off NordVPN on my android, Sonos app worked perfectly. Then I was able to set a split-tunnel setting in NordVPN so I can continue to run it in the background while also using the Sonos 2 app, and this worked, as well.

This may not apply to the problem you’re experiencing but wanted to share it just in case. Best of luck in your search for a fix. I know how frustrating it can get!

Thanks… and I am back to the same issue. My monthly reinstall and re-initialize all of Sonos speakers again. Sadly I don’t even bother with support anymore just re-install everything. No need to respond just registering how frequently this happens.

When they’re not discovered in the Sonos app, can they still play if you press the play/pause button or use AirPlay or ‘direct control’. If so I would not factory reset them. Instead try fully closing the App and rebooting your mobile device and see if that perhaps fixes things?

Thanks Ken. Yes they can still play except Sub Mini showed a question mark. Before I did a factory reset I closed the app and rebooted my Samsung s23 several times. I download the Sonos app again, reset the Arc and paired, then it said I need to re-register. I tried and it continually returned an error. I tried a factory reset on the Sub Mini. I closed and restart the app. First 2 times nothing showed, third time it recognized the Sub Mini. It added the Mini and then pushed me back to registering the Arc. Once that returned another error it didn't add the Arc or Mini. Patient wearing thin as this app seem very buggy and inconsistent. 

The SONOS units are impatient. If there is a communication issue, perhaps due to WiFi interference or network traffic stalls, the SONOS unit or controller will give up. These events leave clear tracks in the diagnostics — unless you have Factory Reset before submitting the diagnostics. 

@Seamur88 

This is what I think is perhaps the case…

If the speakers are still playing audio, or capable of playing, without opening the Sonos App, then they are okay and probably all (from their perspective) is working as it should be - so (please) do not  factory reset them each time, as that’s not ever going to solve the issue. It’s likely doing more harm than good.

The issue you appear to have is "SSDP Multicast Device Discovery” - in brief, your controller device/Sonos App is using SSDP (part of the UPnP protocol)  to initially discover the Sonos players, multicasting via UDP to 239.255.255.250:1900 and, for good measure, broadcasting to 255.255.255.255:1900. Thereafter communication is unicast. At least that’s my understanding.

In your case, this discovery is failing across your network setup and it needs to be resolved - it can be something on the mobile device that is causing this. It can be the router and/or it’s settings, or it could be network switches, or other wireless access points that are not allowing the multicast packets to get through to the destination.

If this IS your issue and I suspect it is, then factory resetting your Sonos speakers will never resolve this in the medium to long term. You (and others, myself included) need to try to find the cause. In some cases that may be a simple settings change, or in perhaps a worse case scenario, it might mean a new router.

I think at the moment you’re looking in the wrong place, trying to solve this and I suspect the real answer lies elsewhere.

Have you discussed this issue with Sonos Support at any point and has multicast device discovery been a part of that discussion? 

@Seamur88,

Your comment mentioned earlier …. "Bizarre update. After 4 hours of trying to troubleshoot I restarted my phone (although I did this multiple times) and for some reason the pairing worked and the speakers are connected to the app again."

….this is a classic example of a ‘discovery’ issue - I’m wondering already if there are multiple wireless access points within your local network, as my initial thoughts here are, that the phone was perhaps connected to one access point, or WiFi band, one minute and things were not working ….and then later connected to a different wireless access point, or band, the next minute and the Sonos devices were suddenly discovered. 

Another explanation perhaps is the phone was initially connected to a guest WiFi network, or using its .LTE connection, or using WiFi Calling etc. and later established a correct local network connection.

The above are just some very simple things/suggestions/explanations to provide you with examples, but there are lots more things to consider before ever choosing to reset a Sonos device.

Thank you very much @Ken_Griffiths. I really do appreciate the extra time to reply with this valuable detail and help troubleshoot with me. I will try your recommendations hopeful that I am successful. Again this is very much appreciated.

Ah that’s okay.

Just post back at some point in the future with a little detail about your local setup, such as…

• Make/Model of Router (NB: an online link to user manual is quite helpful too).
• Make/model of anynetwork switches, or wireless access points.
• Channels & Channel-Width in use on each access point.
• Make/Model/OS of controller device.
• Sonos products (state if any are wired to the LAN and if so where to).

Then we can perhaps begin to see where the issues may lie.