You need to share the folder using the SMB v2 (or higher) protocol and ideally give a user/account on the PC permission to access the folder as ‘read-only’. Then add the network UNC path to the mobile Sonos App with the user/credentials alongside that has the read-only access.

Here’s two Sonos Support links and a YouTube video aswell, that each will hopefully perhaps assist you to setup Sonos access to the share…

https://support.sonos.com/en-gb/article/share-your-macos-music-folder-with-sonos

https://support.sonos.com/en-gb/article/add-your-music-library-to-sonos

https://youtu.be/kjhKhDuvgDY

Thank you! I was finally able to do this using the Networked Device option referenced in the video.

I was using the other options before.

I have tried all of the options suggested in the video but I still can’t add my music library to Sonos app on my MacBook Air computer.  I continue to get the message “Sonos was unable to add the music folder”.  Access denied - check the username and password.  What gives?  Very frustrating 

Have you given ‘read-only’ permission to a user/account to access the SMB v2 (or higher) shared folder? If so, then ensure that the user can access it over the LAN and that you have entered the user account credentials correctly in the Sonos App. Note that both SMBv1 and HTTP shares are no longer supported.

I had to select the Networked Device option to get this to work and type the path.

Ex. \\My-Mac-mini\MUSIC

Yes I’ve given permissions and also selected network option.