Sometimes when the gateway dictates that a particular CC is not allowed, it doesn't update the Secure Payments form and the setting needs to be refreshed. To fix this navigate to the Core:
  1. Click Settings > Payment settings
  2. Click the Payment Services Tab
  3. Click Edit into the Payment Gateway being used for the form that is not working correctly
  4. Mark the checkbox for the credit card type you do not want to allow
  5. Re enter the password
  6. Click Save
  7. Click Edit 
  8. Unmark the checkbox for the credit card type you do not want to allow
  9. Re enter the password
  10. Click Save