Is the cart pushed all the way down flush in the connector?? if it is you can adjust the pin on the connector up with a jewlers screwdriver.The cart might be touching the top of connector and shorting it out.Is the kick settting flush on top of the battery?
Did i read your post right,you are using a 16490,16500(18490 and 18500) batt in the legacy???Have you tried adjusting the
throw on the switch by adding the supplied washers,one at a time.The switch might not be connecting.I know i had to add washers to mine.