Hello @DTMW, welcome to the Sonos Community!
I am sorry to hear that you are having trouble indexing the Music Library from your Mac to your Sonos System.
As you were most likely told by our Support team after trying the troubleshooting steps available, thank you for reporting this to us.
We are investigating the issue and do not currently have an ETA on when this will be fixed.
I will make sure to reply to this thread with an update, when I get one.
For anyone else experiencing this, please reach out to our Support Team for live troubleshooting.
I hope this helps.