Student Discount Germany

[kfm]

I tried to get the student discount (50%) offered by UNiDAYS. I have followed all the required stepts but Spotify won't change my subscription. This is the error message I get when I try to claim the discount: Wie es aussieht, kannst du das reduzierte Produkt, das du kaufen möchtest, nicht erhalten. Du kannst dein Konto trotzdem gerne jederzeit auf Premium umstellen. (In English: It seems as though your cannot get the discount package you are trying to buy. You can, however, update your account to Premium any time). The things is, I already have a Premium account. How do I go about it?