I created a book in iBooks Author (very easy), and uploaded it using iTunes Producer. However, I didn't realize I needed to create a separate sample book/publication preview. Now, when I look at my book in iTunes Connect, it says, "No publication preview uploaded. You must upload a publication preview before it can appear on the store." However, I can't find any way to upload my publication preview after the fact. Interestingly, in iTunes Producer, it says "Optional Preview", so that's why I didn't worry about including it. I click on "choose", then navigate to where I saved the sample book file, and it is greyed out so I can't select it. I did try starting from scratch, but it still didn't include the preview. If I save the preview in iBooks Author's default location, then I can't find the files anywhere on my computer, so I just saved it in my documents. Any ideas?