To connect to the ISS Expert, uPnP setting in the NVR and manual Port Forwarding to the router are required.

However, if you set only those settings, ISS(IDIS Solution Suite) Expert will give a private IP address of the NVR to ISS client over WAN network, and you will not be able to connect the NVR with the private IP address.

In this case, FEN service is the solution for the problem.

Register a NVR to FEN Server, FEN server will pass the both of IP addresses of NVR such as public and private to the client, it will make the client access the NVR correctly.

Then the Network configuration diagram looks like this.