How can i verify my payment method when everytime i do it, it always says “please try again later”

• You may have an unpaid order. Find out how to pay an unpaid order.
• Contact your financial institution. 
  • You may need to ask your financial institution to allow international purchases on your debit or credit card.
  • If you want to know why a debit card, credit card or other payment method has been declined, speak to your financial institution. Apple doesn't have information about why the payment method was declined.
• In some countries and regions, your payment method may be declined because of changes to local law. Find out about billing and purchases in Europe or what to do if your card is declined in India.
• Still need help? Contact Apple Support.

In this case you can reach out to apple support team directly to get it fixed Official Apple Support