These books are currently not available for different reasons. Some are being revised. Some are from a program that Amazon no longer has.
Amazon no longer has their Fan Fiction platform, Kindle Worlds, available. I had two books up for sale with it. They both hit Best Seller.
These books are older books that have been around for a while. They are getting revised with new covers and a round of proofreading. Nothing major will change in the story. Just giving them a little love.