Go to mojang's official website, login to your account, if the login fails, click on restore/recover password.
Make sure you are in control of your account so you know the right email and the right password.
Once that's sorted, go to the client, login with the EMAIL and the password. Things should be fine now.
Make sure you're using NOT the Win10 client to connect to noobstown, but the JAVA of pc/mac client