I have a 1994 1/2 HP Professional Line Liftmaster garage door opener Model number HWB0777 The sending infra red light was not lighting. I replaced both eyes, with another brand, now both light up and so does the green LED behind plastic control button of the wall unit. I have 5V to door eye and 9V to wall control unit. I pressed and released the green learn button on the unit but the green LED does not light up. Do you any idea what the problem may be? Thank you, John