When charging a customer, where the customer is present in the payment flow (Customer Initiated Transaction), coming PSD2 regulations require that the card holder is strongly authenticated (e.g. 3D Secure), except for some exemption cases. Read more about PSD2 here: https://blog.reepay.com/psd2-strong-customer-authentication/ This will affect the use of saved cards for easy checkouts, as the card cannot be used without Strong Customer Authentication (SCA) in the card holder present scenario.
To remedy this, Reepay Checkout now offers an option to start a checkout charge session with a saved card (card-on-file). The customer will be sent directly to Strong Customer Authentication and directly back afterwards with success or error indication. In some cases SCA is not necessary, so the customer will not be prompted with any request for information during the payment session. See: https://docs.reepay.com/reference#card-on-file
Notice that Merchant Initiated Transactions, that is payments initiated by the merchant (or a party acting on behalf of the merchant - e.g. Reepay), where the customer is not present in the payment flow, are out-of-scope for SCA. In this scenario payments with saved cards can still be performed using the Charge API (https://reference.reepay.com/api/#charge).