Laguna CNC Z-stop not working

Very new to CNC. My company got two Laguna IQ 2x4 CNCs that I have been tasked with figuring out. I can not home either of the CNCs. They will go to the top of the z axis and keep trying to move up and the CNCs will not be able to home. I’ve taken the casing of the top of the spindle and can see the light activating when the sensor comes close to the z-stop but the gantry will not stop. Is there any way to fix this? Any advice would be appreciated