I'm experiencing a similar issue, where all media devices are on their own vlan, but the server running the software and the hdhomeruns (2 x quatro) are on a different vlan.
I can access the tuners using emby or channels without any issues, but the hdhomerun software on appletv or firecube won't see the devices, yet sees the dvr server which is on the same vlan as the quatro's so there should be no reason for it not to work.
Unable to find Tuner if not on the same Vlan as TV - walkerx
Re: Unable to find Tuner if not on the same Vlan as TV - walkerx
What are the IPv4 and IPv6 addresses of the Apple TV and Fire Cube?