It might be something simple, man.
First of all, is there any plastic film yet to be peeled off inside the tube or contacts?
Second, did you perhaps screw the 510 cap and switch on the wrong ends? This is known as "reverse assembly" and allows the 510 cap to sit atop the extension tube, rather than in it's designated place, the part of the body without the ring. Reverse assembly isn't possible without a
Chi You replacement cap, or some sort of
insulated and conductive spacer , because the switch will not make contact with the tube like the 510 pin does, it won't reach.
Third, how curved is the closed end of the inner battery tube? It may be so curved, that nothing but a button top battery will make contact, in which case I'd say it's fine to use a magnet spacer on the positive end of the flat top battery that goes into the tube first. There's nothing for it to short to on that end, so use whatever you need to bridge that gap if that's the problem.
All Hammer clones can be iffy, most notably with the spring loaded 510 pin, with the exception of the Hcigar one, which is GREAT.
I've had the Hcigar one for something like seven months now, and still vape it with an Origen or Magma on top it while at home lounging. I've replaced the 510 cap with the Chi, the switch works great except for the thin azz locking ring that can be difficult to grasp with big fingers, but with the way it sets down and the fact I don't pocket it ever, means I never have to lock it. Performs great, with awesome ergonomics. I still love it and super happy with it.
Cheers