We accept credit cards as a payment method for subscriptions. You'll need to leave a credit card on file for Clay to charge. If you're having trouble with your Revolut card specifically, you may want to try using a different credit card, or please ask to speak with a human agent who can better assist with your specific payment situation.
Source:Clay: Terms of Service
Hey Panos, thanks for reaching out and sorry to hear you're running into this issue. Are you using a credit card from Revolut or which payment method are you attempting to use?