Hi there!
Please check your order on XBOX.com to ensure that your order went through successfully.
Go to Microsoft.com and log in with your account. Then, click on your name in the upper right and click My Microsoft Account.
On the next page, scroll down to order history and locate your preorder.
If it says anything other than Completed, then something went wrong with your order. Please contact XBOX Support for further assistance and information as to why your order failed.