I'm not familiar with the 7104 NVR - but if it works the same way as the 76xx and 78xx with cameras not recognised on PoE ports, what has worked OK is:
In the NVR web GUI, pick the PoE channel that you have the camera on, change the mode to 'Manual' instead of 'Plug & Play', note down the IP address used by the channel.
Change the IP address of the camera to be the same as the PoE channel you have selected.
If you can't connect the camera to the LAN to use SADP to do this, as PoE is the only power you have, connect the laptop/PC cable to a spare PoE port and use SADP to set the camera IP address.
That usually works OK.