To rest it to factory., please do the following:
Remove the charger from the Kindle and hold the power button or switch in the OFF position for about 20 seconds.
Release the button or switch, then connect the charger and try to turn on the Kindle.
If this doesn't work, please repeat the steps and this time hold the power button or switch in the off position for a full 40 seconds. This should reset the Kindle to factory defaults. You will know that it successfully reset to factory defaults, if it reset the Kindle back to the way it was when you took it out of the box. Did it do that? If not, please try it again, being sure to hold the power button for a FULL 40 seconds. If it did require you to set it up again, then the factory reset was successful.
If the information that I have provided has been helpful, would you mind taking a moment to rate my service? I'd really appreciate it! As an independent contractor for just answer, I do not receive credit for my answer and I am not compensated in any way without a rating. If you need more help, please tell me exact model of your Kindle. If you're not sure, please look for a serial number.