Connect XVR IP camera system with Nighthawk MR2100 M2

I have a XVR camera system (herospeed.net) that I could successfully install locally and by wiring the XVR to the router with an ethernet cable and port forwarding. However, I cannot manage to access it remotely.

I have tried using P2P, UPnP and DDNS without any luck.

I would like to know if it is actually possible and compatible to install the XVR with the Nighthawk MR2100 for remote access and if it is, which protocol should I use?