We recommend that you contact your bank to check if they are aware of any issues, if not simply submit your question via the app. One of the most straightforward reasons your credit card could have been declined is because you've reached the credit limit on the card that was set by your card issuer and the company simply won't let you borrow any more money until you've made a payment.  If you have another card, the safest option is to go to the Balance screen and change your default credit card to the new credit card.