If you managed to control the Camera with a seperate control unit it suggests that the camera and cable are fine. I'd say it will either be the settings on the DVR (camera address, baud rate etc), the RS485 wires are crossed on the DVR, try reversing them. Or the data output on the DVR is faulty.
If you have a multimeter you could put it across the RS485 output and expect to see typically between 0 and 5v DC. Try moving the camera with the meter connected to see if any voltage is present.
Another option is factory resetting the DVR as suggested above. Set it up again and try it.