Ok, but do you have ePub or PDB ebooks from B&N? This method works with EPUB files only.

If you get the "B&N User Key not found. Unexpected DB format?" error, you can try to remove the "ClientAPI_v012.db" file, then re-authorize BNReader with your account information. Alternatively you can use the key-derivation script (ignoblekeygen). Both ignoblekey and ignoblekeygen will produce the same output when they work correctly.

Also make sure you use the name from the Credit Card, not your B&N username.

If you need to remove DRM from PDB files, read the following thread:
Remove DRM from PDB ebook from B&N (Barnes & Noble),...