Hi there! My name is*****'m sorry that you're having this issue. It would be my pleasure to help you resolve this.
This problem and many others are often the result of a "glitch" in the software. Luckily, it is easily fixed.
I usually recommend starting with "Remove the charger from the Kindle and hold the power button or switch in the OFF position for about 20 seconds" but you've already tried it. (Note: This is what you attempted, but it didn't work for you).
Since that didn't work of you we will need to move on to the next step, which is a factory reset. If you do have to reset it to factory defaults, you don't have to be concerned about losing your books. The books that you have purchased from your Kindle will continue to be available at the Amazon website under My CONTENT if you should wish to download them again at some point in the future. You may however lose any "side loaded applications that you have on your Kindle Fire. If you don't know what these are, you probably don't have any :).
Remove the charger from the Kindle and 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.