Sonos has removed support for SMB v1. This is the reason why most users have “lost” access to their music library. If you have a NAS, enabling SMB v2 or 3 should fix the issue you are having. 

You can also try resetting the app and reconnecting to your system if you have SMB v2/3 enabled already.

There are a few posts here, with fixes for the same issue. If you have your library on a PC, Mac or NAS, just do a search.

Thanks for the reply but I have no idea what you mean by NAS, SMB, etc.

What library cant you find? I assumed you were asking about a local library where you would store your personal music files.

Do you have music files stored on a PC or Mac?

Locally held libraries are working in the new Sonos App as long as the local files/folders are being shared using SMBv2 (or higher) sharing protocol. SMBv1 and http shares are no longer supported by many major companies now, including Microsoft, Apple, Google and Sonos. They are considered to be a security risk so those risky protocols are not in the new Sonos App.

Read about the SMBv1 issues here and elsewhere online:

https://www.tripwire.com/state-of-security/smb-protocol-explained-understanding-its-security-risks-and-best-practices