Al wrote:
I have a Craftsman Garage door opener with an external keypad.

Suddenly the external keypad does not work. I have replaced several
batteries and that does not seem to work.

How do I reprogram or make this functional again?

There's usually a button on the opener you need to press in order to
program the keypad. (Get out your ladder and take a look.) Try pressing
that button and then entering the new code on the keypad.