Mastercard gift card declined on Apple purchases

I recently had gotten gifted a 100$ Mastercard giftcard and it will not let me use it on apple, I used it for smaller purchases and it has worked. I even tried to buy the apple thingy so it would add money to my apple account and when I try it, it just says my payment method declined and to try again later. If you have any solutions PLEASE help me because this is really annoying!

[Re-Titled by Moderator]