I installed a backup camera and it only operates during the time period when the truck has the headlights automatically shut off (because it’s day). Once it turns night, the reverse input still works but it says there is no signal. My theory is this is an issue with the ground wiring of the camera. Camera used was a Boss Audio License Plate Bracket Camera (Included Wiring Diagram)

 

That's a very simple setup. Use a volt meter at night when the camera is inoperative. Verify operating power at the camera while using the ground connection at the camera. It's doubtful there is an issue with the video connection and its ground because that would be affected at all times. My guess is that you have your power circuit improperly wired.