Ensure that;

-you have entered the correct PIN code.

- each key press is being registered with a beep sound.

- you must press the C button before and after you have entered your PIN to 'Confirm" that your PIN is correct. The first C is to clear the entry form in readiness for your PIN, and the second C is to confirm your PIN is correct.

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Try repeating a few times, sometimes the number does not register if not pushed down hard enough. You may need to experiment a couple of times to find the right pressure for pushing down on the buttons.