What is 3D Secure payment authorisation?
3D Secure (3DS) is an additional authorisation for online card payments that helps fight against fraud. If a merchant requests it, you'll receive a push notification asking you to confirm if you're authorising a payment.
If you didn't receive a push notification, you can open the Revolut app and an authorisation prompt should appear there automatically. You must be logged into a Revolut mobile app to complete the authorisation.