Instant On + Code redeem = No download on console

When you say that it fails, what's happening?

Have you managed to redeem the code for the game?

Does the download start at all?

Are you seeing any error codes or messages?

Have you tried doing a full reboot of your console, assuming you use instant on mode?

As M3tal stated, you can buy them from Xbox.com or console, in order to ensure 100% security.

Otherwise, you can buy them from third party websites such as Amazon, BestBuy, Walmart, Gamestop, etc... in which if available, it will show "Instant" or "Download Code", in where you will receive an email with the Code to redeem the game online.

There should be a code included inside the box that had the console. Then you simply redeem the code from the console and the download of the game should start.

How to redeem codes:
support.xbox.com/.../redeem-prepaid-codes

(Relevant section: Redeem prepaid codes on your console)

What code did you redeem? If it was for prepaid currency it should be added instant to the account you redeemed the code on. Could it be possible, that you was signed in with another account?

Hi, assuming you are signed in on your Xbox with the account that redeemed the code, it may or may not have automatically installed on your Xbox depending on whether your Xbox is in instant-on mode or energy-saving mode. If it didn't automatically install,
it should be waiting in the "Ready to Install" section of your "My Games and Apps" section. For full information about viewing and installing downloadable games/content: https://support.xbox.com/games/game-setup/view-downloadable-content

For more information about instant-on mode and energy-saving mode: https://support.xbox.com/xbox-one/console/learn-about-power-modes

Also, make sure you're signed in to the account on which you redeemed the code, and make sure you see the redemption of the code reflected in your order history at https://account.microsoft.com/billing/orders

Hope that helps!