Why is payment not working in the app?

The reason why a transaction has not been successful will be highlighted in red when a payment fails.  Typical examples of why payments fail to be authorised are listed below:

The expiry date is not valid: 

The card will be declined if insufficient funds are present to complete the transaction and you will be prompted to use an alternative form of payment

Many banks now require additional security checks, and you may be asked by them to complete further authentication to verify your identity.  Should authentication fail you will receive this message: