EXACTLY, THIS MADE UPDATE WORK!!!! THANK YOU!!!! TURN YOUR WIFI 5.0 OFF and only allow 2.4 wifi TO BE USED ON YOUR ROUTER. As soon as i did this update started. 

THIS IS THE SOLUTION FOLKS, THIS IS THE ANSWER!!! IT'S SIMPLY TRYING TO USE YOUR 5.0 WHEN IT NEEDS ONLY THE 2.4 ACCESS. 

This worked for me. Power went out last night and my entire ARC with surrounds and sub disappeared. Followed this (have nest WiFi too) and the system showed back up. Thank you and to Sonos, fix your damn product. This is despicable.

This worked for me. Thanks. 

Unfortunately switching to 2.4ghz only hasn't helped. 

Couldn't be more disappointed, I don't have hours to troubleshoot. If I pay the premium it should work flawlessly. As others have said, seriously considering selling it all up. 

I (fortunately) only updated App on one device (iPhone) and it was giving me the “devices not available” message. Old app still worked on non-updated devices. On updated iPhone I could see the “your system” screen for a few seconds when turning on app before going to the “not available” screen.  After a few days of frustration and searching for a solution I was about to give up ( I have 13 Sonos devices). I happen to be looking on the iPhone with the update app and after a Oh, what the “Heck” moment did something that allowed it to work. Hopefully this may help a couple of you. I won’t claim this is THE solution, but I’m hoping it may at least help a couple of you. Enough typing.

Go to account setting on Sonos app (top right, person in circle).

In account setting, scroll down to App Preferences.

In App Preferences, scroll down to and tap Reset App and click on Reset.

I got the message that it found all my devices not being shown before on the update and reconnected them through the app.

Again, hopefully this may help some of you.  Good luck!.

4th of July miracle? After utilizing a fellow member’s advice I was able to see several missing products only to have every device in my system (9) disappear about a week ago. Fortunately they were all still working with Alexa and my surround sound, but still a major pain not being able to group or search in the app, yet still didn’t find a good time  to go through the reset process. 4th comes around and we are having a bunch of people over so I thought I need to get the app working, open it up, and lo and behold my entire system is there!! For the last two days everything has worked perfectly, Bluetooth switching, grouping, everything. Is it too good to be true?

Please ignore my previous post. My entire system is gone again. This blows.

Amazingly if I use “Home Assistant” app all the Sonos products appear immediately and are controllable. This then sometimes allow the Sonos app to find the products