Trouble with Kindle Previewer?
If you work on a Mac running OS X 10.11 El Capitan (or have just installed Kindle Previewer on an older Macintosh operating system), you might get an error when launching Previewer for the first time. In fact, you probably won’t be able to launch it.
Apple stopped including the legacy Java 6 runtime back with OSX 10.7 (Lion), so this problem occurs with Mountain Lion, Mavericks, Yosemite, and the new El Capitan.
Here’s the link:
Quit any other applications running Java before installing. This should do the trick.