The hand held remote control for my garage door opener is no longer activating my door to open or close. The battery is fine. We had a glitch one day when using the mounted panel in the garage to open the door and since then the remote will not work. We have recently moved into this house and there are no instructions on the garage door opener. I need to know how to reprogram the remote so that it will work again. The opener is a Sears Craftsman 1/2 HP unit.