Plex Client and Server in Different Subnets

Hello Guys,
I desperately need help .

I will explain briefly,

Router C is acting as gateway. I configured static routes from router A and B to C.

I am able to ping and traceroute from either side of router A and B using my laptop.

But the shield is NOT recognizing the server.

I have added the respective subnets to the "allowed network", "authorized network" in plex config.

Can anyone please tell me any workaround for this? (like portforwarding or something?)

Any help is greatly appreciated.

Thanks.
Robot

Note : I am a Noob in networking