Without knowing any more than that my first response is that if the proximity sensor LED is activated then it must be working, at least enough for that to occur. What does it trigger in the control box? Is there a relay out, loose connection, etc.? Are the sensors hard-wired in or do they have connectors? If they have connectors maybe you can switch the Z for X or Y and see if it triggers when the sensor activates. Just make sure you switch them back!
David
David