HI there. My name is***** am sorry that you are having this problem. I will do my best to help you. In a case like this, the best thing to do is to reset the Kindle Fire to factory defaults. (out of the box settings). 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. Any side loaded apps and data may be lost. If you aren't sure what that is, you probably don't have any.
Let's do the following:
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.
If for any reason, the device fails to reset, please try this alternative method to restore it factory.
Sign in to Amazoncom. Go to My Account > Manage you content and Devices and click on the device tab. If it is available, you'll see REMOTE FACTORY RESET as an option in the drop down menu under DEVICE ACTIONS. Please note: The Fire’s battery needs to be charged to at least 30% and it must be connected to a Wi-Fi network. If this doesn't work, or of the option is not available for your Kindle, please let me know. Thank you!