Maybe see if this thread (with screenshots) from Sonos Staff will assist you to get things working…

Hi Ken, unfortunately, all of these steps were already in place and verified more than once.  Share permissions shouldn’t be a problem as we are connecting with admin.  But even with other users having the right connections, the last step is where it all goes wrong.  It just won’t connect and keeps on giving error 1002 ...

1002 is some kind of network error - have you tried connecting by using the NAS IP address (and path) instead of its netbios name? Maybe try it with SMBv2 only set for both min. and max. settings - check the cable to the NAS too and maybe try another cable. That’s all I can think of - Oh and use the Sonos mobile App to setup the path/user credentials, rather than a desktop controller App.

Yep, both NAS IP address and server name has been tested, no difference.  Working via the Sonos mobile app doesn’t seem to do much: it says “Unable to connect to folder”, but at the same time tells me it might take a while so I should check later. Still no result after a couple of hours, so I guess this doesn’t work at all.

I tried playing with the different settings on SMB versions, about any possible combination of SMBV1, V2, V2.1 and V3, for both minimum and maximum settings.  No difference, it still won’t connect, BUT, once any of these values were changed, the error code switched to 1001.  Restoring to the original setting (min=V2, max=V3) did not change back to 1002, the error code seem to be “stuck” at 1001.  I tried with a new shared folder on my NAS, same story.  Next, I did power-off/on my Sonos Connect box, and found that the error code was again 1002.

Further I found that my NAS was on a different IP-segment than the Sonos Connect boxes (I have 2 of them), so changed the NAS IP-address, still no success in adding its music library.

As I was experiencing several connection issues with Sonos apps from 2 seperate desktops and mobile phone, I finally decided to power-off my full network (modem-routers) and multimedia environment (TV, Sonos, Plex, Apple TV, …) with exception of the NAS.  After powering up again, I restarted testing, and by some kind of miracle, the system became accessible and is now updating the music library in my Sonos desktop app.  Since we have restarted modem etc on several occasions in the recent past without any success towards the music library, it must have been a mixture of issues where the final step was to reboot some stuff.

So finally, without an understanding of what exactly caused these troubles, it seems that it is working again after more than 6 months …

Thanks for your thoughts …

Hope this might give some hints to other people experiencing the same issue …