Sometimes things go wrong when jailbreaking or messing around. So let's fix it!
First, lets figure out if your Kindle is actually bricked
If this still does not work/did not fix your issue, it is safe to say your Kindle is bricked.
You have a few options now:
Unless the physics that apply everywhere else on Earth are suspended in your house, your Kindle has now restarted
Now, we need to gain access to your Kindle's filesystem with a computer!
DO_FACTORY_RESTORE and restart your KindleIf your Kindle is MTP, you will need to install either the Amazon Send to Kindle App or OpenMTP. You should now be able to follow the PC instructions.
Follow these steps at your own risk
This is where things start to get complicated. You absolutely follow all of these instructions at your own risk and accept the responsibility for any consequences of messing it up.
Hopefully this Debricked your kindle! If you still need support, join the Kindle Modding Community and open a ticket in #questions-and-support!