Hi
Basically the camera and parking sensors work as a system and if one bit fails they all down tools, the thought process being it is better to tell you that you are doing things without their help than let you bump into something because one bit was not working and you were relying on a warning that never came 🙂
You need to get the codes read which should identify the problem area. In my case it showed a faulty front parking sensor but it was in fact the front bumper wiring loom feeding that sensor (identified when changing sensor did not fix problem).
Good luck