The symptoms you’ve described suggest that the remote requires line-of-sight to the same router, access point, or mesh node connected to your RoonServer machine.
This usually means that the broader network is failing to forward multicast traffic as Roon expects, since multicast traffic carries Roon’s device announcements between remote and server.
Where is the RoonServer machine connected in the network equipment list you’ve described? The more information you share about the network topology, the more equipped we’ll be to troubleshoot this case.
Also, where is the MOCA box configured? These ethernet-coax adapters have caused multicast forwarding issues with Roon in the experience of some team and forum members.
Try enabling multicast forwarding in your router settings administration page for the ASUS and any other managed network components.
You can find our general network recommendations for Roon here: