There is still another explanation. I have a kindle and I have been playing around with the purchases of my own books, seeing how long it takes for a purchase to show up. When I make the purchase on Amazon it does not show up until I turn on my kindle and actually download the book. In one case I waited 2 days before I turned on my kindle. As soon as I did, the book showed up as a sale.
I bought a copy of my book, downloaded it to Kindle AND read it. And still no sales. Several people, several TRUSTED people, including family members told me they bought it, yet still nothing is showing. I am just wondering if there is any way to be sure we are being credited for our sales?