The likely cause is that a banned credit card is being used for a demo transaction. Demo transactions are still sent through parts of our fraud system, and will therefore get caught with this error. Make sure you are not using all 1’s for the credit card number and also make sure that it does not begin with ‘411′. Using sequential numbers can also cause this error to occur, such as using 123456789. A safe one to use for testing is ‘597910143452349′ or any other random number that fits the above criteria while still consisting of 15 or 16 digits.