My friend wants to migrate his minecraft account which was made after 2012 so he needs to login with an e-mail. We want to play realms together but when he puts his info in for migrating, the button just says checking info for half a second and then goes back to migrate account button. But when he puts his username, it says incorrect username or password, he uses his e-mail login when the button just goes back to being a button again. I hate that button. Well, anyway, any help would be appreciated, thanks!
I had the same issue when Minecraft migrated to Mojang global service a few years ago.
The fact is you have two possible logins for Minecraft:
The first one is on the Minecraft website.
The second one is on the Mojang website.
Try connecting to the Minecraft website first, make sur all information are valid (try to connect using user name, then try to connect using email). (I don't remember if there was an option to migrate from the Minecraft website so if someone remember feel to to edit.)
If both worked fine, then try to connect on Mojang website using the email or the username. The login is case sensitive so be sure you did not forget that on the username.
If you still can't connect to the Mojang website:
Try creating another account on the Mojang website (you do not need to buy Minecraft again), then try to add you Minecraft information with that account (in the profile settings).
If both of this did not work, then you should contact the customer service.
The work around I gave you was the manipulation the customer service made me do when I contacted them 3 years ago because I had an issue with the migration too.