You have damaged the system beyond economical repair. There are so many components inside that have fried that it is impossible to repair. Sorry. That's what happens when you overvolt an electronic circuit.
It sounds like the Infrared LED are not on (there are 8 of them on the fornt of the unit), it should automatically turns on when it senses dark scene. You can find out at night using the digital camera pointing at the LEDs, you should see white glow on your digital camera.
The problem can be caused by the power supply that supplies the power the LED assemblies or the detector circuits that suppose to turn on the LED when the surrounding area is dark has failed.