I always take out the battery before switching pills, especially in the twist CL1H models. If you don't and you just take off the bezl, swap pills, and screw the bezel back on you might crush the pill. You should always take the battery out and loose then body from the head so the pill can be fully seated and bezel screwed tightly onto the head. Then insert the battery and carefully tighten the body so it makes good contact, but doesn't crush the pill. If you crush the pill and damage it, no light. If you left the battery in the wrong way you could have friend the pill, no light.
Did you smell any burnt electronics smell?
Also if you shorted something the battery's protection may have kicked in and you might have to wait for it to reset.
The CL1H is great as it is very modular, but you have to know what you are doing with it or you can put things together wrong with destructive results.
EDIT: Do you have the instructions for each of your pills? If it's the 2SD that has hi/low via twisting the flashlight I believe the battery was + towards the tailcap. For the 3SD it's + towards the head. Can you confirm if you used it with the + facing the head before? If you did, that could explain why it was dim with the 2SD...