The customer’s card issuer declined the transaction because the CVV entered was incorrect. The customer should double-check the CVV (the 3-digit code on the back of Visa and Mastercard cards, or the 4-digit code on the front of American Express cards) and try again. If the payment still fails, they should try a different credit card or contact us to make payment manually or us other payment methods eg bank transfer or paypal.
For some card issuer especially Commonwealth Bank credit cards can have two different CVV/CVNs: one for the digital version of the card and another for the physical card. Customers using a CommBank card should make sure they’re entering the correct one. The Commonwealth Bank digital card page explains which code to use (see the FAQ section further down the page).