Hey @Graham_Lovell — Thanks for reaching out!
Just to clarify and make sure we are on the same page —Your Mac core is not able to see the Devialet as an available endpoint in Settings > Audio, correct?
May I ask that you please provide a brief description of your current setup using this link as a guide.
Make sure to describe your network configuration/topology, including any networking hardware currently in use, so we can have a clear understanding of how your devices are communicating.
Have you tried a different USB cable? Are you able to see the device connected to the Core outside of Roon?
Have you tried power cycling the Core machine and endpoint?
Can you confirm whether or not you have any active firewall or antivirus on the Core machine? If so, does disabling them yield any changes?
Thanks,
Dylan