I have several C120 and C320WS cameras, connected to two different subnets on my network.  Lets call them main network and secondary.  

All of the cameras are denied any internet access, regardless of network, however the half that are on my main network are visible through the Tapo App on Android while I am connected to the main network, the half on the secondary network are not.  If I switch, that switches.

I have a server on the main network that pulls a feed from the devices, and it can connect to all of the cameras, regardless of network. I have firewall rules in place to allow communication between the IP of the server and the secondary network, no port restrictions.  

I attempted to open communication between the two networks with all of the ports ive found listed for the cameras (80,8080,443,554,2020,8800,20002,19381,19382,3478,3479) but that still doesnt let the app see across the subnets and I am not sure why.