Microsoft Point Help?

Ok so all i need is 400 MS points. When i try to get them all it says is that my payment info could not be authorized. So i added my other card and the same message came back up. I know for shure both of my cards have money. And the funny thing is that I got the 800 MS points with ease but not even a minute later when i try to get these points it said it could not be authorized.