WARNING! Key to be invalid, denied return

I bought this key, delivery took a little (you get the number code on a card in a little box visikartengroßen, packed in a large cardboard box surrounded by packing material - not very environmentally friendly for something you could also send e-mail ...)
Then the surprise: The Key is explained by Microsoft as invalid. Microsoft Support consists of automatic responses that people are not to be found there. I tried to cancel the purchase, sent a also proof photo, but got neither my money back yet another, functioning key. Whether it is now up to Microsoft or to the seller, I can not figure out. In any case: never again!