Open Settings on your Kindle
Tap Device Options
Tap Reset
Confirm the reset
If the screen is frozen, press and hold the power button for about 40 seconds
Release the power button
Wait for the Kindle to restart
If your Kindle has physical buttons, press and hold the power button until the device restarts
If needed, charge the Kindle for at least 30 minutes before trying again
For a factory reset, go to Settings
Tap Device Options
Tap Reset to Factory Defaults
Confirm the reset