Log into your settings area in Amazon then you will find that there was an 'update' in your book. If you are sure that you've downloaded the book successfully on several devices but you still can't sync them to the furthest location, a high possibility is because the version of the book you downloaded are different. Step 4: Check if the book has an 'update' version Account changed, all books in kindle library will also be changed. But in fact you should know that, all your books are saved in your Kindle library which are linked to your account. Somebody will think that the book has been downloaded to the device already, so even though I log in with another account or use other family member's account, this book will be still in the device. Please note that only by registering the same amazon account can your Kindles be synced automatically. If it is connected to the internet, but your whispersync is not turned on, delete the WiFi connection and reconnect it please. To allow automatic syncing, we must keep our device connected to a wireless network. Step 2: Check whether the wifi is connected or not. If you still fail to sync across Kindle devices and apps, please continue to read and follow the troubleshooting guide below.

Go to Settings > Other > Whispersync for Books. Open the Kindle app and go to Settings > Whispersync for Books. On the Kindle Android app and Fire tablets: Go to Settings > Device Options > Advanced Options > Whispersync for Books > Enable. You can also check the 'Whispersync for Books' settings on your Kindles. Once activated we can go to the furthest page as well as any bookmarks, jighlights and notes. This means you don't have to do anything to get it up and running on your Kindles.

And 'Whispersync for Books' is enabled on Kindle Fire, Kindle devices and apps by default. This setting will help sync our books automatically. Set ' Whispersync Device Synchronization' to ON under Device Synchronization (Whispersync Settings). Visit Amazon official site and log in with your own kindle account, then go to 'Manage Your Content and Devices' and select the 'Settings' tab. To keep our kindle library in sync, we must turn the ''whispersync for books' service on. How to Turn on Whispersync Settings for Kindle Step 1: Enable Whispersync Device Synchronization on Amazon account.

The official guide to sync non-amazon books across Kindle devics and apps How to turn on whispersync settings for Kindle

Kindle personal document service.