If it locks with the keypad suspect the tiny switch underneath the unlock button. Take a magnifying glass and look at the tiny legs that attach it to the green circuit board. There is a good chance the the solder has come loose on the outer/ left hand upper one. That is the one nearest the corner of the board. I've had 2 go like that and it just takes a few seconds to reflow and add a new dab of solder. Worked for me. This connection takes all of the force when you push that switch with your thumb. That's my theory anyway.