Try this please> Go to Amazon.com and sign in with your email and password, then choose register device.
Deregister your Kindle from your Amazon account if it is registered to the wrong account or if you no longer want to use it to purchase books, periodicals, or Kindle active content.
To deregister your Kindle, your device must be connected to a wireless network.
Important: After you deregister your Kindle, the device will be deregistered from your Amazon account and you won't be able to access items stored in your content library or items previously downloaded through your Kindle reading applications.
After deregistering, you can register your Kindle to another Amazon account.
These are the steps from the kindle home screen.
When you deregister and then register that will be corrected also.
you need to deregister the device, and then register it to your account.
From your computer:
hows it going with the kindle? Do you need more help?