First (and I know it's obvious) make sure it's not in lock mode. I'm not trying to be funny or condescending...
I have seen a few posts on other forums about issues with this
mod not firing. They contacted Greensmoke directly (a guy called Danny or Denny I think I remember) to report the issue. Rather than messing with it and maybe invalidating any warranty it might have, I would suggest you do this first to see if they can help.
I know some may suggest messing with the insulator in the 510 connection and that may well be an option if GS cannot help.