When you just log into the account do you get the ’none’ option so that you can try removing the card and then re-enter it’s details from scratch ? If using an iOS device have you tried using your computer’s iTunes instead ?
For a card to have a chance of being accepted it needs to be registered to the same name and address (including format and spacing etc) that you have on your iTunes account, and have been issued by a bank in the country where you are (and therefore the country which is on your iTunes account).