antigone c

Hi All, PLEASE HELP!!! I have bought the Color Video Monitor. It worked alright for 3 weeks, but now when I am switching on it says 'NO CAMERA'. I tried everything, went to Menu, there're 4 options: Vol, Brt, Cam Display 1 2 3 4, Add/Del Cam. I'm trying to push Cam display nothing's happening and I'm trying Add/Del it shows CAM SET UP add camera, del cam1, del cam2, etc. But again nothing is happening, I've tried to push all the button. I really dont know what to do now. I dont need to add any camera, and i dont even know whether handheld and camera is in one channel, cuz there's no option given in the camera set about channel.
If anyone knows about it, please helpme I'll be very gratefull. Thanx a lot in advance! Anty x