Problem with redeeming a Mojang code for minecraft on windows 10

When you redeemed your Java Minecraft on Mojang, you have gotten a 5x5 code to redeem Minecraft on the Windows 10 store.

This redemption is a separate service of your Mojang account, and it's possible to use a Microsoft Account email that is different from your Mojang account email.

Mojang (which gives you Java Minecraft) is separate from the Microsoft Windows Store App, which uses a Microsoft Account email when you redeemed that 5x5 code.

After redemption of that code, the Windows 10 Minecraft is tied to the Microsoft Account email you used on your Windows 10 PC. From then on, you don't really need the Mojang account anymore, if you only want to play on Windows 10. You will then get the game
from the Windows 10 store only, with the E-Mail account you used on the Windows 10 store during code redemption.

So make sure you are signed in with the Microsoft Account email (which might not necessarily be the Mojang account email) when you use the Windows 10 Store app to re-download your Windows 10 Minecraft again.

Players who already have the previous PC or Mac edition of Minecraft (running on Java) can
download Minecraft: Windows 10 Edition for free.

Note You'll need to get a code from Mojang, the game developer, by signing in to your Mojang account before attempting to redeem your code for Minecraft: Windows 10 Edition. Otherwise, you
may incur a charge. To get your code from Mojang:

1. Sign in with your Mojang account.
   
2. Under Minecraft: Windows 10 Edition, select the link to request a code. Microsoft Windows 10 will open.
   
   Note You'll need to sign in to or create a Microsoft account. If you sign in, use the Microsoft account you use to sign in to your Xbox account.
   
3. If you're running Windows 10, you'll be able to download the game right after redeeming your code. If you're running an earlier operating system, you'll need to come back to Microsoft Store once you're running Windows 10.
   

The code you receive from Mojang will be kept on your account, in case you’re unable to redeem it straight away, or in case you have problems trying to redeem it in Microsoft Store.

For more info:
https://support.xbox.com/en-US/games/game-titles/minecraft-windows-10-edition-faq

I am trying to redeem a Minecraft windows 10 edition key from the Mojang website.

This is the prompt I am trying to redeem from:

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Minecraft for Windows 10

You bought Minecraft: Java Edition during a period of time when Minecraft for Windows 10 was included for free. Claim your redeemable gift code by clicking the button below and follow the instructions. As you
might have guessed, Minecraft for Windows 10 can only be played on Windows 10.

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It allows for users who have purchased the java edition of the game to then redeem a code for the windows 10 edition of the game.

This is the error message that pops up:

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Error! It looks like we've temporarily run out of gift codes for Minecraft for Windows 10. Don't worry though, more codes should be on their way. Please check back later!

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Thanks for any help!

I am not an expert, and I have the same problem. I first bought the "Minecraft: Java Edition", I wanted to use the redeem code to get "Minecraft for Windows 10", so I clicked "Redeem", I got the code, but when I entered it, it said "The code has already
been redeemed.", I checked my order history, it said that I had bought "Minecraft for Windows 10" using the code, but when I clicked install, it keeps showing me a small window with my code. I then checked whether if the account/email on Mojang, Minecraft.net,
and Microsoft Store, it was the same. So I don't get why I can't install "Minecraft for Window 10".

The migration process only transfer Mojang account information, that has no relationship with Minecraft windows 10, the account that redeemed the code for the bedrock edition it's the account that will have the access to it

Your order history will show the purchase because a code redeemed it's a game purchase