PayPal returned API error code 10548 - Invalid Configuration. This transaction cannot be processed.
This error usually occurs if you don't have a business account. You must have a business PayPal account within a PayPal Payments Pro-enabled country to use the Direct Payment API. The absence of a home or customer service phone number on your PayPal account can also trigger this error.
If you have a PayPal Payments Pro account and you get this error, check your PayPal account profile and make sure it includes a home phone number or a customer service phone number. Update your profile if necessary.
See the Developer Portal for a complete list of NVP/SOAP API error codes.