I had the same issue with the membrane not responding. So i peeled back and moved the switches around while operating the buttons and it began to work. M assumption is one of the tactile switches gets shorted "on" and the microcontroller wont accept inputs. Also found a couple of pages that show service testing and which tactile switch on the j1 ribbon cable controls what. for example the start/cancel buttons are contacts 10 and 6 on the J1. A off position is an open and closed is 10k ohms. This makes checking the contacts and testing for shorts easier. Remember to remove the ribbon from circuit board when testing. Hope this helps