Check to see that there is a bright LED light on the side of your photo eye.  The light signifies that the photo eyes are on.  On the opposite photo eye, you should see another LED light.  Different brands have different color lights.  The light shows that the two photo eyes are connected.  Depending on brand, the LED light may be dim, not on, or blinking, which means that the photo eyes are not aligned, or it could indicate that there is a problem with the wiring.  In which case, please contact us so we can get this resolved!