The bottom line: After you set up an SMB share as a music library, wait an hour. Problems go away.
The details: I recently set up my Music Library (a samba share on a Linux server). Sonos connected to the library, scanned it without error, and I was able to browse the library just fine from the Sonos app. However, whenever I tried to play any files within the Sonos app, playback would fail with a variety of errors that changed from minute to minute (“Content is unavailable,” “Permission denied,” “Connection timed out”, etc.). Also, none of my album artwork was visible, even though it was stored in “folder.jpg” files for each album in a separate folder.
An hour later, after making no changes, all the problems vanished. Album artwork was visible, and all files in the Music Library were playable in the Sonos app.
Moral of the story: wait an hour after adding & scanning a Music Library. What’s Sonos doing during that hour? Beats me. Maybe it’s analyzing every MP3 file for secret messages.
