A. Is it a Red Laser or an IR laser, Remember you won't be able to see the IR laser with the naked eye.
B. Is the gold colored battery contact tab in the back cap snapped off? In this case the back cap will need to be replaced or fixed. If inside the warranty timeframe please call to setup a return. If outside the warranty a new back cap can purchased on our website, or over the phone.
C. How long have you had it? Through a lot of usage the back cap can get worn down, and sometimes you may just need to purchase a new one (if outside of warranty period).
D. Perform a paperclip test. To do this will you need a metallic paperclip or wire. Remove the back cap and leave the batteries in place with the Positive side facing up while the laser is pointed down. Unfold your paperclip, touch one side of the paperclip to the positive side of the battery still in place in the laser, while touching the battery, touch the other end of the paperclip to the body of the laser. If you are using a Red laser you should see a red dot flash on the surface the laser is pointed at. If you are using an IR laser, put phone camera in selfie mode and place on flat surface. Holding IR laser an inch or so above camera, press down with a pen on the black portion or in case of vibration activated laser take a pen or something and tap the rounded back cap portion. As long as battery is installed, if laser is functioning you should see a red splash in your phone screen.