Same here...though I didn’t take the update until my library was gone and I just keep getting Error 1002. I fixed it in the past but so far no luck this time. Says to reboot my products. So I guess I embark on disconnecting 20+ devices??? This is utter junk. Thought I was past all of this but Sonos must have received another kickback from streaming services to encourage local library users to abandon our own music?

According to the public financial records that Sonos releases, per US government rules, Sonos receives no kickbacks from any streaming companies. 

Because every company literally line-items every vendor/supplier in their 10Q and don’t just lump in Sales/Mktg or other Rev Ops? Sure, Jan. The continued updates clearly penalize only local libraries.

I haven’t noticed any substantial penalties on my local library, which I play daily. Some minor issues, sure, but I haven’t been unable to play it. Stored on a WD NAS. 

I updated to 16.3 and lost my ability to access the Music Library again. I can update it but not access it all.

Odd. What did Sonos Support say, when you called them to discuss it? It’s hard to imagine any change in SMB would impact things on an upgrade from firmware 16.1 or 16.2 to 16.3, but I suppose that ultimately depends on what you ‘upgraded’ from. I’m assuming you’ve reset the ‘share’, per the instructions in the controller. 

 Are you Mac or Windows?  Lost my Windows test share after 16.3.3.  Had to start over with a different Local User account and a different music folder on the desktop with Properties/Sharing shared to the new Local User account.  Not sure this was necessary, but I also mapped the music folder to make it appear as though it was a network device.  All unnecessarily complicated.

I’m on a Mac desktop.  Two  techs at Sonos took over two hours working on this issue (via remote control of my computer) and couldn’t solve it.  THEN, I thought “what the heck, maybe it’s something in my music library”.  Well I wen through it and some tunes had broken links in the library, and some had what looked like name in the cyrillic alphabet.  I deleted those and Voile’, the library attached and Sonos has access.  Yes, it is unnecessarily complicated when all I want to do is play tunes I already bought and paid for. 

 Seems like an index should just ignore bad files and finish the index.  Then allow you to look at a log showing you which files failed to index.

I noticed in my music services my Music Library NAS credentials had disappeared after the latest update 16.3

I added them back and now it works again.

I have had no luck. I, also, had a techie take control of my system but the best they could do was make my MacBook the library server, and not very effectively. I want my NAS-based library back. I haven’t listened to my own saved tunes and playlists since May! I add the library but SONOS never sees anything there. 

 What brand NAS?

I have a Buffalo drive, 2tb.

My music library reappeared and started to work on my iPhone/iPad sonos app in late September. “Yay!”, I thought.  But just this week (circa Oct 7) the library once again vanished from the phone/iPad app, and nothing i can do seems to bring it back.  The library is still visible on the desktop app though, so I can play from there …. 

This seems  like a clown car development process ….. I feel so sorry for the developers that are trying to get this stuff to work, and hatred for the management that doesn’t seem to care ….

BTW I am using a WD Mycloud NAS, attached to a wired network, which is connected by my router to wifi. And as I’ve noted it works fine for my desktop apps, but not for the ipad/iphone.  And the desktop apps connect to the device over wifi. 

My library works nowhere. I did manage to add some of my library to a new folder and sync it before it stopped recognizing ANY folders. A weird open window that closed pretty quickly. 
I have a Buffalo NAS and SONOS support finally admitted that there is an issue with that brand that needs to be addressed. They also said that there were no issues with other brands. I guess that you can prove them wrong there, IanGra.

A couple of weeks ago,I spoke to a SONOS tech who acknowledged, finally, that there was a known issue with Buffalo NAS drives. The issue was fast tracked to the engineering team and, lo, two days ago I got my library back, working as it always did. 
The app still has problems. I can’t browse my large library easily because there is no alphabet key, but third party SonoPhone does what the first party SONOS app doest’t, so it’s all good. 

“what the first party SONOS app doesn’t”