I just received a GPN-1 unit for Nikon D7000. I followed the instructions to mount it to the hot shoe, identified the right connector cable and plugged the cable in the GPS/Remote slot, inserted the other end of that cable into the GPN-1, switched on the GPN-1 unit. But the LED on top of the unit did not blinking. I tried to turn on and off the camera and reseat the cable couple times. Nothing make the LED blinking. Any suggestions? Kerry.