Hi, hope I can help as a one year Halo Triton user.
It's simple. It's either the tank or the coil.
Put that coil on another tank. (Please tell me you have another tank, and another battery!!) If it doesn't fire, the coil is shot. If it does fire, then that first tank is broken. Most likely the center conductor wire broke.
If you have a multimeter, or a techy friend with one, they'd be able to tell you in 3 minutes. You should have continuity from the base of the tank to the side of the inner chimney, and continuity from the bottom center button to the center of the chimney.
The coil can be tested as well. Go from the center bottom to the side. It should be between 2 to 3 ohms, depending on which coil you have. The standard is 2.2 to 2.4 ohms.
Problems might happen if you twist stuff together too tight. Remember, everything Halo is just snug. Don't tighten it like it was a lug nut!
Replacement coils can be inexpensive. I got them from VapingMe for a third of the price of Halo's.
Kanger T2 Sunfire 70mm Long Wick Replacement Atomizer Coils 5-Pack - VapingME.com
I been using them for a month and can detect no difference, except I could buy 3 times more for the price!
I have not found a vape store near me that carried these coils. And you might get a dud.
Check out Joe13's excellent thread on Halo coils in the Halo section.
http://www.e-cigarette-forum.com/forum/halo/545751-triton-coil-complete-rebuild.html
And best of luck!!! You are a Halon!!!