If your card is declined at checkout, it usually means your bank has blocked the transaction. This can happen for many reasons (fraud checks, insufficient funds or card restrictions).
First, double-check the details you entered (name, billing address and postcode) and try again.
If it still fails, contact your bank and ask them why the payment was declined. They can normally see the reason immediately.
If you still can’t place an order after confirming with your bank, contact Yojin live chat with a screenshot of the error and the email you used to order.