This could be a problem with the rules or IPs allowed to connection. For example, a router might give you different IPs based on the connection method: LAN, USB, WiFi, etc.
Double check to see if there are any portforward rules and assign new ones for the IP on the iPhone as well.
As a reminder, you also have to be connected with the iPhone to the same network that the cameras are connected as well, then you can use the NVMS7000 to watch the streams.