Why do my light gates give incorrect results?

Why do my light gates give incorrect results?

LogIT World Support solution: The main reasons Light Gates give incorrect readings is either the Software has not been correctly setup or  using an incorrect interrupt card.  Light Gates only record something passing through them and do not have additional intelligence.  Basically test the light gate by passing an object through it and the LED light on the side should illuminate, also, the software should register something passing through.