If we decline a card payment as a precaution, you may see a Was this you? prompt on that transaction in-app. If you select No, your card will be frozen to stop any further attempts, and we'll review the payment and follow up.
If everything looks right: once you've checked your recent activity, you can unfreeze the card yourself. Go to Cards, select the card, select Edit Card, then select Unfreeze Card.
If you don't recognize the payment: keep the card frozen, see Disputing a Card Transaction, and contact Support.