I had the same problem with the key for my Hundy, well, kind of.
My ignition key is a different cut than my doors. Bought it that way. I guess the previous owner had to replace the ignition key at one point. My valet key will twist in the door lock, but not in the ignition.
Anyways... The buttons on the 3 button master key didn't work when I first bought this rig either. So I had to have 2 sets of keys, my valet key to get me in and the 3 button master to drive all the time.
Sooo... I bought a new battery for the key, still didn't work. Then I had to take the key apart, and I re-soldered the four posts for all the buttons.
Amazingly!! All the buttons worked! They way I could tell is after I soldered a button, I placed the battery back in and pressed the new soldered button and if the little red LED lit, I knew it would work on the car.
Now I have a perfectly working 3 button master key. Albeit, just one, hence my thread elsewhere on getting other keys.

Tip if you try soldering, get a very small soldering tip.
