Why is my card not able to add to the payment method

See -> Add a payment method to your Apple ID

Add a payment method to your Apple ID – Apple Support (UK)

• If you want to change your card, you need to add first the new card, then remove the old card.

See also -> Payment methods you can use with your Apple ID

Payment methods you can use with your Apple ID – Apple Support (UK)

fyi: Not all credit & debit cards seem to work with App Store / iTunes Store, try a different one, or preferably a credit card. If your card is not accepted as a paymenf method, you need to contact your bank.

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Have you change Country or Region?, if so you must comply with all regulations described here -> Change your Apple ID country or region -> Change your Apple ID country or region – Apple Support (UK)

Click here for more support and assistance.