There are so many conditions we can say the camera doesn't work.
1.Such as the power cord is faulty, it can't provide the power to the camera. (we can change another working power cord to test it)
2. The power cord is ok, but some thing wrong inside the camera, it can't get power. (connecting the fine power supply, cover the sensor tightly for 10 seconds , have a look on the infrared, if the infrared light have no change, then is proves may some wire inside the camera is loosing. Usually, the lights will turn red in darkness. )
3. The antenna is faulty, so it can't get signal from the nvr(Have another fine antenna to test it)
4. Both the power cord and antenna are ok, but the wifi module which is built-in the camera is broken, this can also cause the camera can'r get signal from the nvr. (Have a network cable for it, and have a test)
NOTE: All the above test must put the camera near the nvr, and without extension cord.
Tips: The cameras WiFi range can reach to 15-30m indoor, more than 50m outdoor. But the actual wireless distance depends on the environment, as we all know that the wall will weaken the wireless signal.