Where is your Music Library?

Without more data, this sounds suspiciously like an SMB issue on an NAS. 

SMB or Server Messaging Block is a Windows function, either enabled or disabled on the PC. Please explain how the Sonos S1 application with my Music Library enabled is functioning correctly but the Sonos S2 application on the SAME PC, configured with access to the exact SAME Music Library will NOT index the exact SAME files in the exact SAME location as the Sonos S1 application.  The S2 has accepted the folder location and clicking on ‘Update music library now’ then accepting ‘yes’ button the tab ‘greys out’ and the word ‘indexing’ along side ‘Music Library’ shows for approximately ¼ of a second then indexing ceases. Same action on S1 DOES update the index, running for some 20 to 30 seconds with accompanying network trafic.  There is no sign of any network traffic during the ¼ second ‘burst’ when asking S2 to ‘update’ !! Why doesn’t an SMB issue affect both S1 & S2 applications?

Well, you provided very little information in your post, which is why I was guessing an SMB issue. And since S1 can only use SMB v1, and S2 uses SMB v2 or v3, it seemed like a possibility. Since you’ve now confirmed that we are indeed talking about an NAS, I’ll stand by my analysis, although I only have the data you’ve provided to work from. 

However, I’m not overly excited to argue the issue with you. Perhaps you may be better off if you were to submit a system diagnostic within 10 minutes of experiencing this problem, and call Sonos Support to discuss it. Perhaps the hard data in that diagnostic will confirm my diagnosis, or point in a different direction. Then you can argue with Sonos directly, rather than just a community member who was attempting to help. 

S1 and S2 have utterly different SMB stacks, as S2 added the ability to handle SMB v2 and v3, which S1 never could.

Given the lack of data provided about your configuration that is all the data I can supply.

There are lots of threads about SMB configs on various NASs, suggest you search for them.

Apologies for being away for 3 days; we have been entertaining visitors.  Have had a a couple of hours to pursue some further searching.  Came across this thread :

This describes my issue exactly!  Simply put, Sonos S1 hardware and Sonos S1 Windows application works perfectly and Sonos S2 hardware and Sonos S2 Windows application DOES NOT build an index from the SAME music library location! Notice that as of 5 days ago SONOS has NO satisfactory solution for this issue.

This is not a hugely difficult problem for a set of competent software engineers to solve.  The starting point is that the problem lies within the S2 hardware / S2 application anot ‘outside’ in the world of SMB configurations] because the S1 hardware / S1 application JUST WORKS.  Therefore, the starting point for SONOS is to COMPARE S1 to S2 hardware and software until they find the DIFFERENCE between the two systems.  Then they can modify S2 hardware and / or S2 application so that it works same as S1 hardware and / or S1 software.  Simple, but I’m not holding my breath because the other thread has been running for 3 months!

Oh, by the way I forgot to mention that my S2 hardware / application DID work same as my S1 hardware / application up until some 6 or 8 months ago.  I didn’t realise that S2 setup had stopped updating the index until I noticed that a new album was NOT added to the S2 index but it WAS added to the S1 index.  So the finger is still pointing firmly at SONOS.

Here’s an idea from a competent software engineer: why don’t you tell use what NAS you are using, what Samba stack it is running, and exactly how it is configured? Us competent engineers often need to know more than a generic error message, like the actual software and hardware the customer is using. We all can predict this is an SMB config issue, but without you sharing your config there isn’t a lot to be done for you.