Sonos won't play music from certain folders on NAS drive.

The challenge is that you’re suggesting that some folders work, and others don’t, which rules out a bunch of “system” level stuff.

If this is the case, I’d be looking very carefully at folders permissions, especially since your computer uses a completely different method to access the data than the Sonos system does.

Thank you for replying. What I don’t understand is why it’s been working perfectly for for the last year or so and now it isn’t. Adding the folders back again seemed to temporarily work but now Sonos can not play them again. I’m not too sure what you mean by “permissions.” Can you elaborate please.

Have you been making any edits to your Music Library? Are you using Schedule Music Index Updates? How large is your library? Are the problem tracks not visible or are there errors as you attempt to play the tracks?

And frankly, it’s not unusual for firmware updates to make unannounced changes to things on an NAS. 
 

No edits have been made.

Music Index Updates are scheduled every evening at 10pm.

Library has 24,000+ tracks.

I have folders split into //SynologyBox/music/A-B, //SynologyBox/music/C-D, //SynologyBox/music/E-G etc. Sonos shows folers C-D and L-O as being empty even though there are files of music shown within them in the NAS drive. Two possible solutions would be to copy the folders and rename them and add them back to Sonos. Or add the files to other folders i.e. add all artists ‘C’ to A-B folder and ‘D’ to A-G. Do either of these sound plausible? And firmware is up to date.

If you remove them all but just add the problem folder, is it still the same?

Not tried that, but that’s a good idea. But thinking about it I’m not sure why it would work as I can not see any music within the folder.

It helps eliminate the possibility of the library index bring full.  Although you only have 24k+ files, they could have large or problematic tags that cause issue with the indexing or take you over the track limit.

That sounds logical too. So annoying that it’s not necessarily 65,000 tracks but 65,000 files that are the limit. 

It's not 65000 files either.  Think more of it like an ‘average' track takes up 1 space - but other tracks with more meta data (some classical music tracks have lots of meta data and very long tags/track names) take up more spaces, thus lowering the amount available.