Issues With Redeeming A Code

I recently got the promotional code I was due from Amazon for pre-ordering Kingdom Hearts 3 via their service. They sent an email with instructions to redeem the code at microsoft.com/redeem. However, once I input the code, I was given the following message:
"Check the instructions that came with your code. You might need to redeem it on a different web page." So, I tried inputting the code via the redemption on my Xbox One console, and I got the same message.

My region settings are correctly configured to the appropriate region, so that is not the issue. What exactly is the problem here?

:)