The wrong PIN has been entered - you can always reset your PIN tries and unblock your PIN in App by clicking on Unblock PIN in the Card tab. Then attempt the payment again with the correct PIN

Your first transaction in contactless: you need to perform a CHIP & PIN transaction first before you are able to use contactless payments

You’ve reached the limit for contactless transactions 

The transaction value is higher than the balance on the card 

Your card is blocked - check the status of your card in the card tab

You have exceeded the spending limits of the card