This incident has been resolved.

Mastercard have confirmed that they have implemented a resolution, and we are no longer observing any issues. The impact appears to have been limited to returning customer journeys (Customer Initiated Transactions).

We are additionally seeing intermittent failures when processing payments which use a Mastercard Network Tokens. We can see the issue originates within the Mastercard system and are awaiting further updates from Mastercard.

Please be advised that customers may experience intermittent 3DS transaction failures currently via Mastercard.