When logging into the game with a Mojang account (or a migrated Minecraft account), please be sure to use your email address, not your username as requested, and Mojang account password
When logging into the Minecraft launcher it asks for your username and password. However, the launcher has not yet been updated to reflect the fact that new accounts are Mojang accounts, purchased through Mojang.com, which uses your email address instead of a username.
It is also possible to receive the "too many failed logins" error when logging in with your username, instead of your Mojang account email address. If you need to reset your Mojang account password, this can be done at https://account.mojang.com/resetpassword/request
Changing this process to make it more clear requires a new Minecraft launcher, which is planned for the next major update, which is tentatively schedule for this spring. Thank you for your patience!
