If you haven't visited WhoMovedMyBuyButton, a website started by Authors Guild, do yourself a favor and drop by. The website is the direct result of multiple author complaints about Amazon's exercise of the nuclear option they exercise to remove the Add To Cart buttons from displays of books by publishers who have "offended" Amazon in some contractual dispute.
When you visit the site, you'll learn about the history of the conflict with Amazon. You'll also gain the tools needed to allow you to track the status of your books on Amazon.
Authors need all the help they can get.