It is unlikely that you can produce older versions of S Note notes (.snb) from a newer .spd file. The app is not backwards compatible and the older devices also had lower resolutions and such, so worked with different kind of images.
This conversion entry was verified by us and conversion was flagged as wrong or not possible.
Usually this happens when the conversion would try to convert different types of data between each other, such as audio to image, or it is not possible because incompatibility between programs, caused by closed file formats, very limited support etc.
If you find entry that you feel is flagged as bad wrongly, please tell us in the discussion below with as much as information as possible so we can fix it.