Decline code 12 is an error code for PayPal Payflow and it means that it was a general decline. Typically these general declines mean that incorrect information was entered at the time of donation. There is no way to determine the exact cause, but it could be one of the following:
  1. Address Verification Security failure.
  2. Incorrect card number.
  3. Invalid expiration date.
  4. Credit card that is no longer valid due to being cancelled.