brand new 6D with a problem.

I've just got 6D delivered from BH as a gift from my wife, but I got a problem.

It won't read the SD card!! I've tried a couple of cards that work fine on another camera, but 6D can't access them for some reason. I am trying to think of anything that I am missing, but I can't think of anything particular I would need to do to prepare the camera for it.

Am I missing something or does it just need to go back?

Thanks guys.