What is 3-D Secure (SCA)?

3-D Secure is the bank-side authentication step a card issuer can require before approving a payment, asking the cardholder to confirm the charge in their banking app or with a one-time code. Under Europe's Strong Customer Authentication (SCA) rules, issuers may require it on subscription renewals too — which is why a renewal can stall on a perfectly good card.

#Why it causes failed renewals

A renewal charges while the customer is asleep, not standing at a checkout. If the issuer challenges it, there is nobody there to authenticate, so the payment sits unresolved until the customer acts — and a system that treats "unresolved" as "failed" will retry, or cancel, a charge that was never actually declined.

#How WallaB.AI handles a challenged renewal

• A challenged attempt is neither success nor failure. WallaB records it in its own state and leaves the cycle open, waiting on the customer.
• It is excluded from every re-charge path. While an attempt is unresolved, no other charge for that cycle may start — one of several independent guards against a double charge on the same billing cycle.
• It is resolved, never guessed. When the outcome arrives from Shopify, the attempt settles as a success or a failure. If it stays unresolved for too long, a sweep confirms the real outcome with Shopify before doing anything, then fails it by timeout rather than re-charging blind.
• A genuine failure then behaves like any other. It enters the normal retry ladder and notifies the shopper — see What is dunning?.

Because the challenge is between the issuer and the cardholder, no card details pass through WallaB.AI at any point; the payment form is hosted by Shopify. Renewals that fail this way are involuntary churn — see Involuntary vs. voluntary churn.