Hello @Michael_Hickey,
Thanks for contacting support , I’d be happy to take a look over this issue with you. Can you please provide a description of your setup using this thread as a guide?
Please also provide a screenshot of your Roon -> Settings -> Audio Page, it should look something like this:
How is the Marantz MCR connected to your Core in this case, over Ethernet or something else (TOSLink/Analog?)
Please let me know the above information when possible.
Thanks,
Noris