You need to generate the ePub3 and the matching KF8 to get your book also properly published on Amazon (always keeping in mind the important point detailed in 2.)
The KF8 generated automatically by Amazon (as they do for ePub2, converting them to MOBI themselves) is lower quality than the one created through StreetLib Write as it won't include Kindle Pop up text and Kindle Panel View features (http://www.amazon.com/gp/feature.html?docId=1000729511), so it's way better to send them their format ourselves.
To do so, you need to upload the KF8 file when publishing your book. We are working on automating this process.
If you hired a Market service to create your fixed layout book, we'll take care of both your ePub3FXL and KF8.
NOTA BENE: For all the book types with images (few or lots) but composed mainly of text, you'll need to create a reflowable book. Otherwise, your book will be blocked on many stores.
If you don't find your book falling in any of these two categories, please contact firstname.lastname@example.org so we can assist you.