I don't have that particular light. Like I said, your next step is to test continuity from the negative terminal to whichever part contacts your battery tube.
You could have a bad switch. Or, your switch could be fine, and it just isn't making contact to (brass?) ring which in turn has to touch the non-annodized end of the battery tube. If so, you need to take an appropriate instrument to un-screw the switch housing (needle nose, snap ring pliers, pointy tweezers, etc) and see if the switch contact is making good connection.
Or, your battery could just be too long, make sure it isn't sticking past the battery tube and stopping the tailcap from screwing on all the way. Sometimes you need to loosen the head some to gain length. But, that works best on bodies that can carry the current through the threads. That model appears to be annodized at both ends.
If you don't have a meter, I would suggest picking up a cheapy. But, you could rig together a test light with a lamp, some wire, and a couple batteries.
The point of the exercise is to find out where the break in your circuit is exactly.