Check the status of your wireless connection. If your Kindle is not connected to a wireless network, you cannot shop for, buy, download, or sync from your device. From Home or any Settings screen, you can view the Wi-Fi indicators at the upper right corner of your Kindle.
Sync to receive your content. If Whispersync is not enabled, or if your Kindle did not receive a book or periodical, try manually syncing your device. To sync your device from Home, press the Menu button, and then select Sync and Check for Items.
Check if you are filtering content. At the top of your Kindle screen select By Most Recent First and press the right side of the 5-way controller to filter items by Title or Author.
Restart your Kindle. Press and hold the power button for a full 40 seconds. After the first 6 to 8 seconds, the screen will go blank, which is normal. Continue holding the power button. After 40 seconds, release the power button.
Regardless, when you select the Books tab make sure to then select the Cloud tab under it. Any purchases you've made should display there. Tapping the book's icon should cause it to queue for download.