It's likely because it's a debit card (whether it does or doesn't work elsewhere isn't relevant, different sites have different validation rules), not all debit card seem to still be accepted by iTunes, and they might no longer be accepted at all in some countries. Do you have another card that you could try, preferably a credit card ?
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).
Or if you don't have a valid payment method you can use these instructions to create a new account and not have to enter payment details : Create or use your Apple ID without a payment method - Apple Support
Why does Apple reject my debit card
