Hi @John_Dickerson,
A number of potential causes can underpin the diagnostic error you received in the ARC tab in Roon, but let’s start here:
I first recommend you verify you’ve added Roon as an exception to the Windows firewall on your Core device by following these instructions.
You’ll need to verify that the Roon executables are allowed through the Windows firewall, namely Roon.exe and RAATServer.exe. These executables will be visible in the folder path of your Roon database: databaselocation/Application. If you need help locating your Database on a Windows Core, here’s a guide.
Second, we’ve pulled routine diagnostics from your account, and there’s some indication that you’re using Roon with a VPN. Note that VPNs will interfere with port forwarding by translating the routable IP assigned to your router. If you are using a VPN, you’ll need to disable it to configure port forwarding and to use ARC. However, if you require your VPN to remain on for other uses outside Roon, note that Roon users are posting workarounds for accessing ARC via your VPN in the #tinkering and #roon discussion sections, like this one: ARC and a VPN - alternative solution?
We’ll follow up with next steps after you’ve verified these first two steps. Thank you for your patience.