Wallet doesn't allow to add debit and credit cards what to do?

Click ▶︎ Can’t add a card to Apple Wallet.

If that doesn’t work, then try linking the payment method:

Open Settings ➢ your name at the top of the list ➢ Payment & Shipping ➢ Add Payment Method.

Once the payment method has been added, you will have the option to link it to Apple Pay.