Was the update an Apple ‘beta’ update, or just an update to iOS v15.3.1? If it’s the latter, I just did that update too and my Sonos system is still working/showing okay here.

My thoughts are to maybe try a quick reboot of your router and Sonos devices to see if that resolves the issue.

Or see if somehow the iPhones lost their settings for permissions for the Sonos app?

it was the Sonos app update. I have restarted router and all devices to no avail. iPhones still have permission too. 

It’s quite possibly an IP address conflict then, arising from the Routers DHCP server. You could try again by powering off all, then bring each device back online, one at a time, leaving things to settle before powering on the next device. I suggest using this order…

1. Modem/Router
2. Wired Sonos Products
3. Wireless Sonos Products (Starting with nearest, then next nearest…)

You should see the devices in the Sonos App, but just ensure your mobiles are connected to the routers main WiFi signal and not a guest WiFi, or other wireless access point etc.(if applicable).

Doing as Ken suggested above got my Sonos working again.

Adding static/reserved IP addresses to my router's DHCP page and doing the power cycle again kept it from happening again at the next update or power failure.

Did what Ken said to do. No dice. No Sonos. 

All my devices are connecting to the same router, too. I can see my Amp on my computer network page (no sign of the 5 there). But my phone only sees my 5 but it can’t connect. 

@roberbaran

This is quite a strange issue, simply because no one else is complaining about the recent update (well, not so far, it seems) and I would expect that if there was a problem with the software rollout.

So I’m just wondering if you have coincidentally had a router firmware update too, that might be causing this issue?  What make of router are you using and does the Sonos system all come back online if you temporarily cable one Sonos device direct to your router?

Yep. my Amp is directly connected to the router by cabling. 

The plot thicken’s… and I’m starting to now wonder if the Amp’s WiFi has been switched off, or it’s wireless/adapter has failed, by sheer coincidence.

Are your local router WiFi settings currently stored in your Sonos App Network Settings? ‘Settings/System/Network/Manage Networks’?

Anyhow…

So the Amp doesn’t appear in your Sonos App, even though it’s on the LAN (SonosNet)? - So can you kindly clarify that you have not factory reset anything here, the Router, or the Amp etc?

Assuming you haven’t factory reset anything so far, I would maybe just quickly try another cable between the Router and the Amp (if practicable)? Even try other Ethernet ports. 

Presumably no security/VPN software has recently been added to your mobile/computer devices?

The final thing to do is wire another Sonos device in place of (or as well as) the Amp to the Router and just see if that causes all devices to return and appear in the App.

Tell us what router.

Got my Amp back by resetting my Sonos App on my iPhone. I will try connecting my 5 to the router with cabling in the morning. 

Resetting the app is only a temporary fix, when the problem comes back, please, tell us what router.

Looks like same problem with my current app update. Was working fine and now all speakers just lost

My reply was two years ago. On the 7th Sonos released a mobile app that doesn’t work for many, I would wait a month or two until they have fixed it.