You have also not really told us what the problem is that you are having other than nothing appears on the LCD which you have immediately assumed is a fault with the keypad function. In your code (at least the code you have shown) My advice is to get one thing running at a time. Perhaps start with the LCD and make sure that it is actually displaying some characters. Then add in a single button press (with debounce) to understand how that works. Then work up to the keypad.
Susan