I had the same issue and what it means is that something is incorrect about your credit card information.
The key puller doesn't work with the new version of the reader, but you can still use the keygen script. You have to use the exact name as it appears on your credit card (especially if that may be different from what you used for your
B&N account). You can also confirm the credit card on file via your B&N profile. They display the last four digits for you there. Once I used the exact name on the credit card it removed the DRM correctly.