A couple of points to consider (while we’re waiting for Roon Support):
- Your Core is on a Synology, I notice that someone else running Roon on a Synology had trouble with Roon not seeing the Denon:
It wouldn’t work with WiFi, he had to have a wired ethernet connection. Which leads to the second point:
- Your Netgear is a managed switch. Roon recommends unmanaged switches. It may be that Roon’s method of network discovery is not getting through to see the Denon.
You can try a few things temporarily to diagnose (one at a time, obviously):
- replace the managed switch with an unmanaged switch temporarily.
- connect the Denon directly to the router (and remove the managed switch for surety)
- Install full Roon on your Mac, and use the Core there to test whether it will see the Denon via the managed switch.