S2 lost access to local music libraries (iTunes and External Drive)

Huh, interesting. Every morning, I listen to a local library using S2, it is data created by iTunes (now called Music), without issue. It happens to be stored on an NAS, but that shouldn’t make any difference, unless something changed without your knowledge (which unfortunately happens frequently with various applications). 
 

I think, in order to get to ‘minimal trial and error’, access to the reason why your system is throwing an error now, which means access to the data on your system by a Sonos employee. 

I would recommend that you submit a system diagnostic within 10 minutes of experiencing this problem, and call Sonos Support to discuss it. Don’t post the resulting diagnostic number here, they get sensitive about GDPR.

There may be information included in the diagnostic that will help Sonos pinpoint the issue and help you find a solution.

When you speak directly to the Support staff, they have tools at their disposal that will allow them to give you advice specific to your network and Sonos system.

Thanks for the suggestion. In general, I hate (even resent) having to spend time on calls with tech support for such things. But, in this case, it actually might be the right next step.

I understand, agree, and sympathize. But from the outside, we’re only guessing, since we don’t have access to the errors it is throwing when you attempt to access it. 

I went simple for my setup, FLAC files on a bare-bones SMB NAS. It hasn't failed to work across updates to Sonos or the NAS system software. The fancy setups should work, mine does.

There was a simple solution this time!

Before calling Sonos Support, I decided to try re-adding my two music folders.

Immediately, I was reminded that MacOS had changed the local host name on my main device. (Because it detected a conflict. I vaguely recall that warning a couple weeks ago).

I changed the name back in System Settings, re-indexed Sonos, and it works now.

So, this time, it wasn’t Sonos’ fault 😀