How do I deregister my Kindle for Android App?
In some cases, the Kindle application may not sync correctly, or may encounter some errors. It is also possible that after a firmware update is applied, you may not be able to register your reinstalled Kindle for Android app.
As a possible fix, it may help to deregister your existing application.
To deregister your Kindle for Android application, go to: https://www.amazon.com/gp/css/homepage.html You may need to sign in at this point if you have no done so already.
From this page, go to Digital Content and select Manage Your Kindle link under the Digital Management category.
From this point, go to Your Computer and Other Mobile Device(s). Click "Deregister" to deregister next to your corresponding Cruz device. Here you can also edit the decription of multiple Cruz tablets to differentiate one from another.
After deregistering, you may then log into (register) your Kindle for Android app with your existing Amazon Kindle account.