Using the Keypad library with the adafruit 1x4 membrane keypad

Hi,
You need to tell it the row connection, that will be the common to Pin 5, not common to gnd.

byte rowPins[ROWS] = {5}; //connect to the row pinouts of the keypad
byte colPins[COLS] = {9,10,11,12}; //connect to the column pinouts of the keypad

Try that... Tom...