Sorry about the inconvenience. We will definitely get it resolved as fast as possible. There are quite a few possible causes. Most can be resolved with a simple troubleshooting step right away.
(If we also supplied the battery, skip this paragraph) Can we ask what brand/type of batteries you are using? The light works with 2xCR123A batteries or 1x Button-top rechargeable 18650 battery. It is recommended to test the light with a new set of CR123A batteries or test the batteries in another device to rule out the battery issue.
Can you test the light with the steps below?
1. Remove the pocket clip if it is installed. (important step)
2. Unscrew and remove the tail cap
3. Unscrew and remove the head from the body tube. Basically take the light apart into three sections: head, a middle tube, and tail cap. In some recent batches, the head is glued to the body tube. If it is hard to unscrew, skip this step.
3. Use a clean cloth to wipe clean threads on the body tube
4. Fully tighten the head to the body tube
5. Install the battery with positive button end towards the front of the light
6. Fully tighten the head of the light and the tail cap
7. Press the power button on the back to turn on the light. Point the light to your palm in case it is set to the dimmest mode.
If it still doesn't work, another common issue is a loose plate in the tail cap. I attached an image to show you how to tighten the plate. The instructions say to use a small screwdriver, but I find that a small pair of needle nosed pliers works better to grab both dents at the same time.
Does the light work properly now?
