Here is a tutorial on how to set this up. I'd check to make sure you have your dropbox linked... I know there were issues with apple and 3rd party data transactions a long while ago...not sure if/how they were resolved.
Also, you are one of several (one-and-only post) people who have come here bringing up this topic. If you are NOT a bot for the OTHER ebook software trying to get free advertising (welcome to MR!!
) then I would recommend using the search function on this forum, or scroll down the list of thread topics.
Cheers!