Exactly the same with me….. just gone. Unplugged from router and mains but still no sign. Anyone any ideas? Thanks.

I’ve now tried several things. The main was signing out of my Sonos account in the app and then login in. At that point the re-install of the boost seemed to work. Sort of. Details:  I’ve completely deleted the app and all data and reinstalled it, tried to add the boost, signed out of my account and then signed back in. That seemed to help sort of. But the new app only recognizes my music library occasionally. When it does, then the app redesign just sucks. No ability to search the music library. No alpha short cuts on the side. Sonos needs to fix this quickly or acknowledge it’s abandoning music libraries that made it what it is, and I’ll turn my attention to something like plex to try to make all of this work. 
 

and taking to social media to talk about Sonos demise. 

I have had to to unplug my Boost and trash it. Previous to the new app update I was using Boost - but with the update none of my products were even being recognized and my system was empty. So I just disconnected Boost… and know they’re back. I was late to getting the memo that Boost was being discontinued.

I realize this isn’t an ideal fix as people were using Boost for a reason, but that’s what I had to do to get my music and speakers back :-(

I had 2 working boosts, one is now missing and the other is not showing in the iOS app. I cannot add the other Boost back to my system. The connected Boost shows up in the web app, but you can't add devices through it. I have the older version of the app on my iPad, but it won't let me add new components. No music without two boosts. I am refusing to update my network infrastructure because of this problem. Everything worked fine before this update. Sonos, you need to fix this now!