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

 Did you try this procedure?  Don’t know how old these instructions are.

Yep, same thing is happening to me after updating to latest MacOS, Sequoia 15.0.

Same issue after updating to latest MacOS, Sequoia 15.0.

Can’t connect to my system from my daughter’s (latest model) Mac since installing 15.0. My Mac is a 2019 with the Intel chip, and that still works. Has anyone with a newer Mac been able to connect?

Found a solution that worked for me on Reddit: https://www.reddit.com/r/sonos/comments/1fiz5cj/comment/lnksluh/?utm_source=share&utm_medium=web3x&utm_name=web3xcss&utm_term=1&utm_content=share_button. Basically, check the setting (Settings/Privacy & Security/Local Network/Sonos) and toggle Sonos on.

I had the same problem, but managed to get things working by going to Manage->Music Library Settings … and adding an additional folder, which had a few random music files in it, to the list of shared folders. After the library had been reindexed, everything could be played again, including material in the folders which had originally be shared. I was subsequently able to delete the folder I had added without breaking things.

The root cause seems to be something to do with the need to add an entry to the Access Control List of shared folders.