That function is currently not available in the new app.  Not even sure if it will ever be coming.

That is diabolical! My "Owned" music is on my discs and PC! I will be reverting to previous version immediately! Thanks for confirming the new App is rubbish!

The only other work around is to use Plex service which catalogues your local music and makes it available to Sonos. You also need to allow external access on Plex so that it can be reached from the internet.
By using Plex you are then reliant on Plex service working, and during internet outages you also won’t be able to listen to your local music library.

The Sonos speakers still advertise themselves on your local network as UPnP renderers, so there are options to send local audio files to the speakers, but for me the Sonos app refuses to be one of those options :/

I can access my network drive library but can't search it and can't seem to put it as the first priority. Bizarre.

How do you map to it? No tab for "Music Servers" in the new App? 

HELP HELP HELP ... has anybody found a simple workaround to access  PC Shares, Network Drives, Cocktail server? 90 % of my music is on these! Get your act together Sonos, this must have affected thousands of Users? Can I revert on Android devices???

See this thread: 

unbelievable...

Good luck with that… Sonos took down that option on Apple App Store.

They could do the right thing, say they made a mistake and put S2 App back up until they bring this new App up to where their ecosystem was on Tuesday.

I have the same problem. I can see the files on in my music library but I can't play anything.

The only option  for Sonos is to roll back to the previous app.

I can't understand how this was not beta tested before being deployed.

Not sure if people are still having trouble with this but I found that opening the Sonos PC App with administrator privileges allowed me to add my NAS drive