Actually, that is pretty normal. I have seen many games that won't use the enter key and even other keys on the number keypad.
One thing you can try is going into the settings within the game itself and see if that key is an option you can choose. Most games give you the option to change what keys you use for what. If that key isn't listed, then there is no way to use it. You would either need to fix the main enter key on the keyboard, replace the laptops keyboard or try using an external (connects via USB) keyboard.