According to Sonos,the problems are always caused by somebody else. Yet those other components are never 'playing up', only the Sonos equipment is being problematic.

The simple answer is that Sonos is no longer fit for purpose.

SONOS has changed the way it uses the network. Some network defaults are no longer appropriate.

Without knowing any of your network details, we cannot suggest much.

FWIW: None of the Community regulars are experiencing your issues.

Are all your speakers wireless? I had a similar problem and connecting some of them via ethernet to the network solved the problem which wasn’t an issue for me since I already had Cat 5 pulled throughout the house.

I’m having the exact same issue. I have 12 devices that all appear in the Wi-Fi  network app but have disappeared from Sonos. Factory reset of a speaker acts like it’s reconnected but as the app notes “may not appear in the app” . . .it doesn’t. Not sure what happened to brick this entire system but it’s annoying, frustrating and ridiculous. I changed nothing on my end and nope, it’s not a network issue. Every other device I have connected to the network works fine. 

I’m having the exact same problems. As are friends of ours. It’s definitely NOT our network and I’m tech educated. I’ve uninstalled and reinstalled more times than countable. It just drops all the time. They’ve done something to their system that no longer works. Unfortunately, I think it’s time to cut our losses and buy a better system that actually functions with our internet face. Bummer, we really liked the sound quality. Too bad there’s no actual advice to fix the issue. And, for the person saying “it’s not us, it’s you”…I don’t think so…it’s def Sonos. 
Best of luck. 
 

If nothing works, is that bad?

I have had this problem so many times since May 6th I lost count.

NEWS FLASH: Sonos has not f****** idea what they are doing. Period.

Moderator Note: Modified in accordance with the Community Code of Conduct.

The problem is with Sonos whether they admit it or not… I continue to periodically try to get it working hoping one of Sonos updates will be the fix…with no such luck.  I have unplugged the router from the wall, unplugged every device (not just Sonos devices) from the wall, plugged the router back in, waited 30 minutes, then plugged everything else back in.  EVERYTHING else in the house reconnected and works fine EXCEPT for Sonos.  My network provider app, shows Sonos devices connected.  My Sonos One (Gen 2) responds to google assistant and will stream iheart radio.  Yet on Sonos app “no system found”.  How can google and iheart respond to the speaker if it’s not connected to my WiFi?  I even turned off cellular, WiFi, and Bluetooth on my iPhone and iPad and it still responds to google assistant…. ‍♀️. Unbelievably frustrating!  

Sounds like the SSDP/mDNS device discovery packets are not working across your network with your mobile device App. There can be a number of different things that may cause this issue, so I’d give Sonos Support a call. Here’s a link to contact them…

https://support.sonos.com/s/contact

 What is your mobile device used for the Sonos app?  Do you have a PC?  If you have a PC have you tried the Sonos app for a PC?  Have you tried the WEB app ( play.sonos.com )?  The WEB app does not fit a phone screen.  Do you have another mobile device to try the Sonos app on?

I use the Sonos app mainly on my iPhone (sometimes on my iPad). Thank you for the tip on accessing the WEB app (play.sonos.com) from my PC!!  It is nice to see “most” of my system there and be able to play and connect the speakers that are listed there.  I downloaded the Sonos app for PC but it will not connect.  “Your Sonos product is not found”… I’ll have to wait until I have a half a day to devote and the right mind set to reach out to Sonos support again for additional support.  Thanks again!  

Same issue here. It’s been going on for months and I’m sick of it! Bag of poop honestly. 9 speakers and I’m lucky if 2 or more at anyone time. Utterly sick of Sonos. Used to be brilliant but nowadays it’s incredibly poor. Move and SL are the least reliable.

Have you spoken to Sonos Support about your device discovery issue? If not, then see the link in my earlier post to perhaps contact them.

Note too that Sonos engineers say that their data shows the new Sonos App has the same, or better, system/device discovery, compared to their previous App - see here;

https://support.sonos.com/en-us/article/the-new-sonos-app-and-future-feature-updates

There are many reasons why the multicast discovery packets may not be working as they should be to locate your devices on the LAN subnet - The Sonos support staff maybe able to help you resolve those issues hopefully, so if not you’ve not called them already, if maybe worth seeing what they say.