Account migration failedIf you receive an error message stating that account migration from a Minecraft to a Mojang account failed, please first make sure that you have typed your information correctly, and that you do not already have a migrated account under the same email address. If you have created a blank Mojang account, or have one from purchasing another game, you will need to log into your account with that email address, and migrate your account that way.
Multiple accounts on one email addressIt was previously possible to have multiple Minecraft accounts linked to a single email address. Currently, only one copy of each Mojang game is allowed per migrated account. For people with multiple Minecraft accounts linked to a single email, this means that you will have to choose which account to migrate. If you need to migrate a second paid Minecraft account to a Mojang account, you can do so under a different email and Mojang account.
If someone has migrated your account for youIf your Minecraft account has been compromised (someone knows your username and password), you would typically restore access by resetting your password. However, if someone has migrated your account to a new Mojang account, you will need to contact Mojang support (see below) for assistance. We can reset the email address on a migrated account back to the original without account verification. For anything else, we will need your transaction ID as proof of account ownership.
Migrated account, but gift codes do not appearDue to the way that account migration works, gift codes purchased before account migration do not currently show in your Mojang account profile. However, they are still viewable under your Minecraft profile.
If you have a question about this, or anything else related to account migration errors, you can contact customer support. Please be sure to leave a clear and detailed description of what your problem is, and what you have previously tried, as migration errors can be difficult to pin down.