Also, when above done, clean the contacts between the foregrip board and the eye board (clean with new soft bristled tooth brush) in the body, make sure they are aligned properly too when reassembling. If that fails contact Kee.The little button works but the big one doesn't? By an unfortunate effect of the design, rainwater and condensation tend to run down the grip and go straight into the switch. Best you can do is take the side off the grip and let it air for a day or two to dry out.