@radrzr,

If it is a three way, you are most likely looking at the satellite switch box, which would have fewer wires than the main box would have. I would recommend that you double check that everything is connected securely to ensure that a loose connection isn't causing this.

Otherwise, it sounds like your wiring configuration may not be compatible with the device.

Check whether the electric line is Single-pole double-throw line, as the device will only work on the Single-pole single-throw line. There are several wiring types used in the US depending on the situation, so I would look into mapping out the wires of your switch to see if it is not a conventional Single-pole single-throw line.