Is the door installed correctly? Make sure that its is not askew and is flush with the casing all the way around. It could be that the connector in the door is damaged if the door was inserted in the wrong position.
hi Hungrykid,
Insert the battery upside down and press down for about 15secs - remove the battery and install it the right way around and then press the reset button on the side of the sensor which should spark it back into life. Had the same issue as you and the upside down battery trick worked a charm for me.
cheers
Mike
I had this kind of issue with this speed sensor. At the end y installed the new battery, and press with mi fingers the sensor as hard as I could :), I think that the battery terminals were not making enough or good contact with the battery.