Depends on ‘why’ it disappeared. For many, it has been fixed.

Sonos has changed the way that their new app accesses audio from shared libraries on the local network. The previous S2 App supported SMBv1 and HTTP protocols for file sharing, but these have known vulnerabilities and are no longer used by Microsoft, Google, Apple, Amazon etc. and all has now shifted to using SMBv2 (or higher) file sharing.  You may need to upgrade your shares… see these links depending on how you share your library tracks…

For MacOS users, see this thread.

For Windows users, see this thread.

Sonos sent out notices both in the S2 app, and in email, about these changes. They also updated the FAQ to reflect the update. While they have stated that the local library system continues to be worked on, I do not expect them to resume use of http or SMB v1, so if your computer uses them, I’d recommend re-adding your share, as is indicated in the controller, where it says ‘We’ve made security changes to supported libraries. You may need to re-add your library”.

If you’re having trouble finding this area in your controller, open the S2 controller, click on the gear icon at the upper right of the screen, then the word ‘Manage’ under it. Next, click on ‘Music Library’, and the page to enter/modify your local library will come up.

If you continue to have issues, I would recommend that you call Sonos Support to discuss it.

Hi - thanks for the advice. Re-adding the library seems to have worked although some compilation albums appear multiple times now rather than just once! I’ll have another go at the settings on my iMac to see if I can resolve that too. Cheers. 

 The compilation mess up happened with the last speaker firmware update.  Eventually they will fix that problem.  At this point you can use Folder view to play compilation albums.  Of course you’ll have to get used to swiping, swiping, swiping.