Before performing the hard reset, make sure to charge your Kindle Fire for approximately 30 minutes. Then try this:
Step 1: Hard Reset: Press and hold the power button for 20 seconds and then release.
Step 2: Power it back on: Wait until the device has completely turned off, then press the power button to restart your Kindle Fire.
If the above doesn’t work, Amazon recommends that you try charging the Kindle Fire longer and then trying the hard reset again.