"//{nas path}/Folder/" is no longer available

This still doesn’t work….

Have same issue with QNAP TS-453Be NAS running QTS 5. 54K track local music library.  Tried downgrading SMB but to no avail.  However I do use Plex and Plex can be accessed as a Streaming Service (just like Spotify) from Sonos.  So its effectively Sonos → Plex → NAS Music Library.  

In the event that it helps, I was getting the same error when using the iOS app to add my new library location.

"//{nas path}/Folder/" is no longer available

...but was able to add it without issue using the Windows Sonos desktop app.

I finally got the indexing to work after changing the file share settings on my Buffalo NAS drive to SMB1.  Like others, with SMB2 enabled, the indexing would fail after 10 seconds or so with the share “no longer available” error message. 

Thanks to this thread for pointing out a work-around.

Hi,

The same problem occurs here. The system with multiple S1 components has been working smoothly for years with the QNAP NAS, which contains approximately 5,000 songs.
Bought an additional Roam SL a few months ago and after installation it gives the same error "//{nas path}/Folder/" is no longer available".
In the NAS log I see that 130 tracks are successfully requested by Sonos, but then it stops.
I started creating a smaller library. That worked once, but the next time - after a reset of the Roam - it does not and I get the error again "//{nas path}/Folder/" is no longer available".
I suspect my NAS only accepts SMB levels 1 and 2.

It is hard to understand that this problem has been known for 9 months and that there is still no solution.

After several hours of attempting to move my music library (~ 20K tracks; 1,650 albums; 100GB) to a Buffalo LinkStation LS210D NAS, I have arrived at the following ‘conclusions’:

1. The error message “//[drive name]/music_folder is no longer available.” is non-specific at best, if not completely erroneous.   Upon successfully adding/updating a new, but relatively small, Music Library I can stream tracks from the NAS on my SONOS speakers simultaneously with the SONOS app displaying the error message; of course the music_folder IS available. 
2. There is some limit:   Current_#_Tracks_In_Library + #_New_Tracks_Added > N that triggers the error message.  Hence, if you attempt to add a large music library at once, you will exceed N immediately.   If you take an incremental approach, example add all albums beginning with the letter A, then B, etc. you will succeed until you get to a point where you exceed N; in my case the letter T. 
3. Once I have arrived at this threshold N, if I delete a few albums from Music_Folder, SONOS will successfully “Update Music Library Now”.  Yet when I copy the few albums back into Music_Folder, I get the error message again.   I did think it was possibly some syntax bug with a particular album folder, but I ruled that out by repeating the threshold test with various other album folders.
4. I think the SMB v1 or v2 may be a bona fide issue, however, it is tangential to the main issue here. 

The bottom line is a developer at SONOS should easily be able to troubleshoot and fix this bug as the problem is easy to reproduce, as evidenced by the number of us reporting similar experiences in this forum.

Get the problem to happen, submit a diagnostic, call Sonos support.

Until they get enough interest in a bug it is not bumped up to a high priority for getting fixed.