Declines can happen for a variety of reasons. When Stripe submits a charge to your bank, there are 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 CVC.
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've previously had a successful payment, a future charge can still be declined by a bank’s overzealous fraud systems.
Most declines being generic, we won’t have much specific information as to why a charge was declined.
If all of the card information seems correct, it is best to contact your bank, inquire for more information, and ask for future charges to be accepted.