Minecraft accounts made past a specific date may remain active as Mojang (a.k.a Legacy) accounts. All Mojang accounts are required to migrate to Microsoft accounts and this is quickly achievable through the Minecraft website. The Migration is required to play Minecraft, as logging in to the game requires a Microsoft account.
Note: Ensure the correct Microsoft account is being used before migrating.
Step 1. Log in to minecraft.net with the Mojang account.
Step 2. Find the Profile tab and select Move My Account.
Step 3. Press Get Code.
Step 4. Enter the code in the box, then click Submit and Start Migration.
Step 5. Log in to an existing Microsoft account or choose Create Account to make a new one.
Step 6. After logging in to the account, choose Complete Move.
Step 7. A popup will show saying Move Complete, The Mojang account will now be migrated to the Microsoft account.