Amazon's Kindle platform is fraught with bugs and inexplicable behavior. When it's not blocking ARC reviews, it's ignoring the final version of an ebook and instead sending out a draft copy.
And when it's not deleting reviews because authors engaged in the SOP marketing practice of connecting with their fans on social medial, it's removing ebooks from sale for literally no reason and with no notification.
Over the past couple days numerous authors have discovered - quite often by accident - that their ebooks have been removed from sale on Amazon.com. The ebooks have not been deleted, and in many cases the title is still available in other markets, but on Amazon.com the buy button has been replaced with this notice:
I have read about this bug in a couple Facebook groups, and on KBoards. It is reportedly a widespread problem affecting a lot of authors, but Amazon has elected not to notify affected authors.
One author on KBoards explains how they discovered the bug:
Last night, I got a message from a reader that one of my books was unavailable for purchase. I thought the customer just had the wrong link, but I confirmed that when I go to the book's page, it says "this title is not currently available for purchase" instead of the price. In researching this, most people who report the problem have just uploaded their book and are told to wait. In this case, the book has been available in the Kindle store since August and I've been selling copies all the way up until yesterday evening. I checked in the Dashboard and it still lists the book as live, even though the actual store says it's unavailable.
With authors only learning they had been impacted after meticulously checking their listings, it is hard to say how widespread this bug is.
Fortunately, one author has identified a possible solution. They reported that making a minor edit and then republishing the ebook is enough to restore it to available status.
It remains to be seen whether that will help all affected authors, however.