Some of the reasons for cancelled operations:
You had insufficient funds. You can check available balance of pocket in the app
An incorrect PIN. If you forgot the PIN, please change it.
Incorrect card details (card number, expiry date or CVC (Card Verification Code). Please check it on the card details screen
Exceeded the monthly spending limit of this card. You can always increase it.
Your card is frozen. You can unfreeze the card in the app.
You used a contactless method (pay pass) for the first transaction at a terminal or ATM. You'll need to insert your card in the terminal or ATM for your first transaction and enter your PIN.