With Guardian Keypads, the keypad does not determine how long to hold the gate open only how long to send the open command. Think of this like having a gate remote. When you press the button the light turns on and stays on until you release the button. Once the button is released, the time the gate takes to close is completely dependent on a timer within the gate motor itself.
In very rare instances it is possible for the gate relay to get stuck and hold the gate open. It is very easy to tell if the gate is being held open by the motor or the keypad. Simply take the keypad out of the equation and see if the gate closes. You can do this by either powering down the keypad or disconnecting the relay terminal block. Both render the keypad incapable of holding the gate open.
Disconnect Relay Terminal Block: http://support.quikstor.com/knowledgebase/gate-relay-connection/
Try the above steps. When you reset power, does the gate close? If yes, power the keypad back up and try a code. If the gate gets stuck open again try disconnecting the relay terminal block. If no, call your local gate technician to have a look at the gate motor.
When you disconnect the relay terminal block, does the gate close? If yes, call QuikStor for further assistance. If no, call your local gate technician to have a look at the gate motor.