If a transaction fails with a response code 20054 (Expired card) despite the card being valid, it may be because of following reasons:
The card's expiration date stored in the issuer's system was incorrect.
The cardholder was issued a new card, rendering the previous card invalid after the new card is activated.
The card was flagged for suspicious activities.
Advise the cardholder to contact the card issuer to verify the status of this card.