This is the feature that you can click on inside a book, and then you can choose to go to the cover, different chapters, the appendix, etc.
It is grayed out, as if it has been turned off or disabled.
Any ideas?
Added (1). I tried that Wesley.It is not working on any of my books, including the ones where it previously worked. Thanks.
См. статью: The Go To feature on my Kindle Fire HD does not work?