To unlock the card, log in to the ZEN app or portal.
If you unblock the card which is added to Apple Pay or Google Pay, it is restored in both services and you can use it without any problems.
ZEN app
To unlock your card using the app, log in, and then go to the accounts view. By swiping up from the bottom edge of the screen, you will expand the card section view. Select the card you are interested in, then press 
. Now you can see all the details of your card. Click on "Security", then select "Unlock card".
ZEN portal
If you want to unblock a card in the ZEN portal, log in and go to the "Cards" section. Then select "Manage Cards". Select the card to be unlocked. After selecting the appropriate card, the "Unblock card" option will appear.