The raised copper rings around the magnets in both the switch and delrin battery piece need to touch for the mod to fire, if the magnet is raised they will not contact and not fire. Also the black delrin battery piece can't be too high, need that copper ring to stick out a bit. I put the delrin piece on my battery and then "screw" it down until the delrin is snug on the battery and the copper ring is sticking out a bit. Hope that makes sense.
I had a 4nine clone where it appeared to have too much glue under one side of the magnet in the switch and would not fire because the magnet stuck up over the copper ring, I had to take the magnet out, clean all the glue and replace the magnet to where it sits below the copper ring. Works beautifully now. I use VTC5's btw, never had an issue, they work flawlessly..
Edit to add: mine is not an infinite clone, so I don't have/need an extra magnet. So my post may be irrelevant, sorry
Yeah, the Infinite somehow uses that extra magnet but not with mine. The second I took that thing out, the Copper Ring on the switch and the brass ring in the delrin insulator with the magnet were able to make contact and it fired. The throw is super freaking long though without that magnet.