The harness is a passive part. We already check the harness works well. You can double check each wire.
Check the harness
Use a digital camera or other device to check the AV input of the TV works well
Use a 6~12V battery (Use a multimeterto check the battery voltage) to make a connection as shown in the following picture to provide the power supply for the camera. Plug the RCA connector into a TV AV input. If you can see the camera image shown on the screen, then the cable and camera works well