If your NVR won't let you use the injector on one port, then you will need to put it on a switch and plug the nvr into the switch and then manually add the camera.
But hopefully you can just plug the injector into the poe port.
That's what I am trying to do, but fear connecting the camera for the following reason:
With NO LOAD on the NVR or POE injector, my meter is displaying 70 volts, 0.0 watts at the entire end of the length of CAT6 on the exterior of my home. I feel as if I connected my camera to 70 volts it would kill it.
However, if I connect my meter directly to the POE injector in my basement, it sees 55 volts, 5.5 watts. I am confused as to why the voltage is increasing to 70 volts at the very end of the run of CAT6.
However if I disconnect my NVR from the POE injector, I see the appropriate 48 volts at the end of the run. So it seems as though having the NVR and the POE injector connected together increases the voltage???
I ordered a Ubiquiti GP-V480-032G POE injector just now as well. I believe that this device is active and not passive, so when it arrives I can test it out next week. Obviously it is a much higher quality POE injector and I have actually used it before, to power an access point for my Father.