You will need to use your PIN for your first transaction before contactless is enabled on your card.
From time to time you'll also need to make a purchase using your PIN in order to verify that it's you before you are able to use contactless again. This is a security measure to protect your account from fraudsters. If you forget your PIN, you can also view your PIN in the App, by selecting "View PIN" under the image of the Zable card on the More tab.
If you do reach your contactless transaction limit, make your next in-store purchase using your PIN to re-activate the contactless function of the card.