If you see the following error for Amazon device: An internal error occurred. This can be caused by a lack of network connectivity, please make sure you have a good network connection.
The possible solution is to deregister your Kindle Fire HD:
- Swipe from the top of the screen to the bottom
- Select “More”
- Tap on “My Account” and the choose “Deregister”
- Register it again.
More information on Amazon Customer Support.