Payments for IMDbPro are processed through Amazon Pay.
A charge can be declines for a variety of reasons. Usually, the error message should provide a hint about the nature of the problem. Make sure to check your name and billing address details you've entered match the information you've provided to your card provider (usually the same address where you receive your monthly card statement).
If the charge is declined, we recommend waiting a few minutes before trying again. If you're still experiencing issues with the charge being declined, we recommend reaching out to your card provider who can provide further details on the charge.