Amazon in-app purchase error, region not supported

I really hope that someone will help me, because i'm really confused right now. So i won a giveaway for 50% off 40 classic packs on Hearthstone. I won 2 times and the first time i used an amazon.com code, but my account is for amazon.de. Then I used an amazon.de code and it was accepted on the website, but when i tried to buy the packs, the app gives me a region error of some sort. I am currently outside of Germany but i hope i can fix this issue nevertheless. I tried using multiple German VPNs but i still got the region error every single time. I would pay with a paypal account, with euros, so it's not a regional credit card or anything, and moreover i was able to buy amazon coins, which can only be bought in uk, germany and usa. What could I do? I'm starting to freak out, I need those packs!!

Tl;dr I can't use a discount code for packs outside of Germany, Amazon in-app store gives me a region error. Please help i'm desperate.