Perhaps the battery is dying. Have you plugged it in to recharge it? Also, have you tried poking the reset button through the hole in the bottom edge?
It's unlikely that your device is fried from the firmware update. 2.1.3 came out about five years ago, and my 902 is still working fine with that version. The problem must be something else (dead battery or corrupted ebook that makes the reader loop forever).
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