I have re-flashed the pi sd with a system image from a couple of months ago and it is now working again. So it was something in that apt-get upgrade that resulted in denied access. I am guessing samba. I have put samba update on hold and will try apt-get upgrade again but before I do does anyone know of another package update that might have caused this before I press the button and have to re-flash the os again. I wish sonos could just read minimserver.

For clarification the Samba version that works is 4.13.17

It’s Samba 4.15 and higher that cause these issues. You can add “unix extensions = no” to your smb.conf and Sonos should be able to connect to the server again. 

That's interesting. I've not tried that. What does it do exactly?

Search the page for unix extensions, it is in several places and seems to be different for the  SMB versions.

https://www.samba.org/samba/docs/current/man-html/smb.conf.5.html

Thanks, I'll have a look.

Adding “unix extensions = no” to smb.conf solved it. Thanks, very grateful.