This happen mostly due to some problem in the firmware. I know you have tried a lot already but please read the following. First reset your Kindle by pressing or sliding and holding the power switch(at the bottom) for 20 seconds. Release the power switch. This will reboot the Kindle. If it still doesn't work, plug the charger for 5 minutes and while it is plugged, try the reboot process. Let me know if it helps.
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