There are a number of reasons why your SmartCard may decline. You should contact the Customer Service Centre on 1800 828 232 (freecall) and they will be able to review your SmartCard Account and tell you why your SmartCard was declined. Alternatively, you can check whether the store has been blocked by searching the Blocked Merchants List.
If you have registered for SMS alerts you will receive an SMS message after the transaction has been declined to show the reason for your card not working.