The issuer's risk engine scored this transaction as likely fraud — but unlike 04/41/43, the card itself is fine. Maybe the amount is unusual, the merchant is new, or the customer is traveling.
Ask the customer to approve the transaction in their banking app or answer the bank's SMS, then retry once. 3DS on the retry often converts these.
A soft decline: the condition is temporary. A retry — later, or with a different method — can legitimately succeed.