This has now been fixed with the new Oxygen OS 13.1 update. It was reported by many OnePlus 11 users and OnePlus finally identified and applied a fix in their most recent release.

I installed the update today and my Sonos speakers are now showing up in Spotify after a couple month hiatus.

My system was working for 3 years with no issues. Now nothing works. I have 9 Sonos devices. All disappeared from Spotify app and won’t come back. I’m using iPhone. Restarted all network devices, updated software on all network devices, deleted and reinstalled Spotify app, restarted iPhone. Nothing works. All google cast devices are still working in Spotify app. All Sonos devices show up in Sonos app. This is incredibly frustrating!

Sounds like it would be. Any chance you rebooted your router while the Sonos were unplugged? 

What fixed for me was going to settings > wifi > wifi assistant then turn on dual wifi acceleration. Connect to the same secondary network as your primary network. Hope this helps as even with oxygen os 13.1 the issue wasn't fixed. 

I sent this prematurely. The Sonos speakers did show up in my Spotify app immediately after I updated to Oxygen 13.1, but as reported by many others, the speakers are there for only a minute or two and then they disappear. 13.1 did not fix this issue.

Hello, just bought this week a Sonos Arc, and I encounter the exact same issue: the Sonos Arc doesn’t show up in my Spotify app (I am in Oxygen 13.1). I rebooted the router and the Arc, and still nothing. 

Can you help with this?

Many thanks

Same here, using samsung S23+ on Android 13. Sonos devices cannot be found in Spotify app. Pretty annoying...

What fixed for me was going to settings > wifi > wifi assistant then turn on dual wifi acceleration. Connect to the same secondary network as your primary network

I've recently switched to a OnePlus 11 and have experienced the issue with my Sonos devices not appearing on Spotify.

However Djhillyd's solution seems to have worked for me.

Thanks dude, you've saved me the pain of having to use Spotify via the Sonos app.

Phone settings? Sonos settings? Spotify settings?

Looking for them but haven't found yet 

Phone settings.

Unfortunately for me, Sonos is now no longer showing as an available device.

Same for me, what finally fixed the issuefor me was going to settings > wifi > wifi assistant then turn on dual wifi acceleration. 

Anyone found an equivalent setting for Samsung S23s? There is no entry in settings for WiFi assistant.

I have the same issue with my ultra 23 and it is honestly making me consider changing. I honestly cant take the admin anymore.  I reset spotify. Beam not discoverable. I rest sonos. Reload beam. Sonos works with spotify. Go into spotify to listen through beam. Beam not discoverable again. I go in sono and reauthroise account. Not working. Go through all settings make sure they are ALL set to the right thing on BOTH apps. Still not working. I never had this issue on previous phones and I'm so tired of trying to fix this everytime I want to listen to music. 

Have you found where this is on an ultra 23? I can't find this setting either ?

On Samsung S23, I guess it's on Settings > Connections > Wi-Fi. Click on the 3 dots > Intelligent Wi-Fi.

I guess it's Setting: Switch to mobile data

I'll chime in on this. 

The culprit in my home is 2.4ghz / 5ghz network sub networking. 

Sonos One Sl

Samsung galaxy s23 ultra

Asus router 

If I turn off 5ghz WiFi the speakers show up. 

I can confirm, as the las comment said, the issue is due to the network mode. My Sonos show up under 2.4gh connection, but it disappears in 5g network.

I just got Sonos speakers for the first time today and I'm having the same issue. Originally I was on a 5GHz only band but I swapped over to a 2.4 GHz band and I still can't get the speakers to show in Spotify. 

This will be a deal breaker for me.

I think I fixed it.

I pulled Spotify up on a tablet and the speakers were showing up there. Once I played from the tablet the S23+ picked up the new speakers. 

I found the issue in a galaxy s23. But something similar applies for other android devices. You should change in the settings of the wireless network to use the real Mac address of your device on that network. (Settings=>Wifi settings=> WiFi config => you must change Mac random to use Mac of the device.) just change on that network.

I am experiencing the exact same issues on my Galaxy S23 Ultra. Sometimes the speakers show up in the Spotify app, but at other times they dissappear. I never had this issue on my old Galaxy S20 with the exact same Sonos setup. Google home and chromecast devices never disappear from the Spotify app, and casting Spotify through the Sonos app always works as well. The Sonos speakers are always showing up in the Google home app, so it's purely a Spotify issue. Restarting my phone temporarily solves this issue but then at a certain point the speakers will dissappear again. 

Whats striking to me is that my girlfriend has a Samsung Galaxy S22 and she is never experiencing these issues, all our speakers always show up on her phone. This to me shows that the issue has to somehow be related to a setting on my phone, and shouldn't be related to the network / router settings. Unfortunately I've not been able to find a permanent solution for this... 

This means your router is not correctly routing broadcasts and multicasts between devices on different frequencies. Either fix the router config, or get a smarter router.

Thank you! I recently upgraded my S21 ultra to an S24 ultra and could not figure out this issue. This solved it for me

What wifi router do you have? Sounds like its a mesh system that doesn’t correctly handle random MAC addresses when your phone switches between mesh points (or frequencies).