Those circumstances certainly suggest that the My Cloud account authorization server, run by Western Digital, is down. Have you reached out to them directly?

No, I haven’t. I got spooked when I saw MY Cloud Home no longer listed as a Music Service and thought it might no longer be supported 

Same here 

Not impossible, Western Digital has been making changes over the last several months, but unlikely without prior notification. Unfortunately, Sonos has no control there. I’d give them a call. 

Had a reply from WD Customer Support informing me that “We would like to inform you that starting on September 20th the existing My Cloud Home configuration to the Sonos app will be removed.
However, you can enable local access and set the folder path containing the music on the My Cloud Home device.”

They recommend I use Samba (SMB) to access My Cloud through the Music Library function. 
This means all my (50+) playlists will be useless

I never used the MyCloud Home as a Sonos music service. From day one I've put all of my music files in the folder Public, had Sonos index that folder and haven't had any issues since then. In short: I've used it as a “classic” NAS, bypassing all the "specialties” of the MyCloud Home.

Why would your playlists now be useless? What format are they? Where are they stored?

Sonos do a pretty great job of dynamically fixing up the paths to music files when the upper levels of the path change due to machine/share changes.

This is the way I used it for years

Using the Music Library  to access the public folder 

Then they changed it so you couldn't use smb1 (or whatever its called)

I was then forced to use the mycloud home service  and now its gone  

Are you still on S1? SMB 2/3 has been supported on S2 for years now. You also don’t need to use SMB at all if the files are on the same PC as the Sonos app.

Yeah unfortunately I'm still on S1 as I have old stuff 

I've read this thread as I have the same problem, but I'm on S2. I don't understand how to fix the connection between Sonos and My Cloud Home. Please can someone write it in really simple language?

You can’t. WD killed the My Cloud service to Sonos on Sept 20.

You need to treat your WD device like a regular hard drive and set it up using the Sonos app on PC.

That's what I mean, how do I get Sonos to play music from My Cloud as if it were a storage hard drive? The email I received from WD said I can continue to use the music on My Cloud via Sonos, by changing the settings/path. I followed their instructions but it didn't work. 

I want to do this - change the folder path and enable local access but I don't know how to!

I originally had a Segate NAS which connected via the Music Library, then that drive corrupted and I was forced to buy a new drive. When I set up the new MYCloud I couldn’t use the music library as before and needed to use the MyCloud Home function. This worked in as much as I could access the files and play the music but all my Sonos playlists wouldn’t work because it was looking for the non-existent music library. The tracks appeared as grey icons. I laboriously went through all the playlists replacing the greyed tracks with their MyCloud Home - blue icon equivalent. I’m now assuming once I manage to connect back to MyCloud through the music library (which is so far proving impossible), I’ll be back to square one, having to reverse all my previous work?

I’m struggling with this. Their instructions involve adjusting the settings on the drive - which I can’t do because it says the connection is ‘Direct’ rather than ‘Local’. I’ve ended up setting up a new ‘local user’ but none of the pathway addresses I put into Sonos’s music library setup work

Solved!

I spoke to Dmitri D at WD tech support today and they talked me through it using remote assistance. I had to use a Windows or Mac PC, open an Internet browser and write a direct address/IP address: http://mycloud-xxxxxx to access the My Cloud Admin settings. Sign in. Switch Local Network Access to On (it was off). 

Then open my Sonos App

Settings

System

Music Library

Music Library Set Up

Add Shared Music Folder

Type the path //MYCLOUD-XXXXXX/YOURCLOUD

(Substitute with your details)

Then Update Music Index.

Hey Presto - my music now plays from 'Music Library'

Can I just check that path?

//MYCLOUD(in caps?)-XXXX(something like 192.168.1.123 or 80AP8AB?)/YOURCLOUD(the name of the folder eg. MUSIC or username?)

I think it's

//MYCLOUD-XXXXXX/the name of your music folder

XXXXXX is the LAST 6 LETTERS/NUMBERS OF YOUR MYCLOUD SERIAL NUMBER FOUND ON THE BOTTOM OF YOUR MYCLOUD

Ahhh!

This almost works, instead of the error message saying it can’t find the computer. I get an error message saying it’s unable to add the music share to the music library (900).

Does it have anything to do with the fact I control MyCloud from a desktop (Mac), where as Sonos is controlled by my phone app?

No, that's not the issue. I use the Sonos App and MyCloud Home App on my phone and tablet. But I had to do the MyCloud fix by computer then Sonos reconfiguration by mobile App. When I was on the chat available from the WD website, they did remote viewing of my computer screen to help me. It really was a good service.

They’ve said they’re going to call but in the meantime they keep sending me links to their (quite vague) How To tutorials.

Did you have to set up a new local user to get Local Access to work?

No I didnt have to set up a new local user. I told them I'd tried the how to tutorials and nothing seem to work and it was too complicated anyway. I was on Chat for 20mins when it dropped out, they them called me straight away. The technician didn't know Sonos and WD had been disconnected, but it didn't stop him from helping me.

Used the WD callback service to finally resolve this issue. Turns out, the problem was Sonos being unable to access the password protected space. Once the files were moved the the Public folder - Sonos could connect - much to everyone’s surprise 

Pathway: //MYCLOUD-xxxxxx/Public

Thank you to everyone who has contributed to this discussion. Like someone above I used a Seagate with music library seamlessly for years. Then the Seagate wore out and I replaced with Mycloudhome. I gave up with the smb issue and used the app rather than the music library which was very inferior.

Then they stopped the app working. 
 

This thread is the answer and I now have music library back . I have spent hours over three years with this. Not sure who fixed the problem but this is great.