Can we ask what brand and type of batteries you are using?
Can you test the light with the steps below?
1. Unscrew and remove the tail cap. Unscrew and remove the head from the body tube. Basically take the light apart into three sections: head, a middle tube, and tail cap.
2. Use a clean cloth to wipe clean both ends of the threads on the body tube
3. Fully tighten the head to the body tube
4. Install the battery with positive button end towards the front of the light
5. Fully tighten the head of the light and the tail cap
6. Press the power button to turn on the light.
7. The lowest setting of the EC20 is very dim and hard to detect in a bright room. Please look straight at the LED inside the reflector while you click the side button.
Does the light work now?