Declines happen for a variety of reasons. When we submit a charge to your bank, they have automated systems that determine whether or not to accept the charge. These systems take various signals into account, such as your spending habits, account balance, and card information like the expiration date and CVV.
Since these signals are constantly changing, a previously successful card might be declined in the future. Even if all of the card information is correct, and you may have had previously had a successful payment, a future charge can still be declined by a bank’s overzealous fraud systems.