Hi there! My name is***** am a computer professional with over 15 years of experience with both Mac and Windows computers, phones, tablets, and printers. It would be my pleasure to assist you with this.
I believe that the best thing to do in this situation is to reset your Kindle back to factory defaults.
Please 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.
Be sure that when you set it up again you use the same Amazon account info (email address and password) that you were previously using.
Next, login to your account at Amazon.com. Select YOUR ACCOUNT. From the drop down menu that appears, please select MANAGE YOUR DEVICES AND CONTENT. On the page that appears next, you will see a CONTENT Tab and a DEVICES Tab. On the CONTENT tab you will see all of your Kindle book purchases. You can sort them by title, author or purchase date. Please locate the book that you want to download to your Kindle, select it by checking it and then click on the ACTIONS column. Choose deliver as the action. Select your device from the Device list. If you have more than one Kindle, make sure that you choose the Kindle that you are actively using. Don't select the Kindle Cloud reader unless you have downloaded the Kindle Cloud Reader APP to a computer or device other than your Kindle and wish to read it there.