Doesn't accept code

[sykomon]

I've bought a gift card for 10€ yesterday.
And I'm Germany and there's a electronic shop called 'Conrad'. I bought it from this shop. The code got activated.
But it still gets denied and the actual message says 'Dieser Premium-Code ist leider nicht gültig. Versuch es noch mal oder wende Dich an den Kundendienst.' which translates to 'This Premium code is not valid. Try again or go to the customer service.'

What should I do to still get premium without buying an other card?

[ErikG]

Hi.

Here's some information on Spotify gift cards:
https://support.spotify.com/account_payment_help/managing_payments/spotify-gift-cards/