Here are some possible reasons:

Declines can happen for a variety of reasons. When we submit a charge to your customer’s bank, they have automated systems that determine whether or not to accept the charge. These systems take various signals into account, such as your customer’s 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 your customer previously had a successful payment, a future charge can still be declined by a bank’s overzealous fraud systems.

Solutions:

  1. Try with a different card, American Express is more strict about security checks
  2. Make sure all details are correct: Name, Card Number, Expiration Data, CVC
  3. Try to create a new account starting directly with a Pro account

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