The issue you're experiencing with accessing Minecraft: Java Edition on your account may be due to the way the game licenses are shared on Windows 10 and Windows 11. Generally, when a game is purchased and redeemed on a specific Microsoft account, that account retains the rights to access the game. In your case, since your father redeemed the product key on his account, only his account has access to the Java Edition.
While the game may be installed on your PC, the licensing is tied to your father's Microsoft account. Therefore, when you log into your account, it does not recognize that you have the rights to play the Java Edition, which is why you see the "Buy Now" option.
To resolve this, your father would need to either:
- Log into his account on your PC to play the Java Edition.
- Share his account credentials with you (if appropriate) so you can access the game under his account.
- Consider purchasing a separate license for your account if he does not intend to play the game.
Unfortunately, there is no way to transfer the license from one account to another, as the licenses are not shared across different accounts on the same device unless specified by the publisher.