Are your passwords stored in the database in plain text? If so, make sure you brcrypt($password) when setting the user model's password attribute. I'm not sure why it doesn't do this out of the box, mind you.
I'd hazard a guess that the reason you're getting the credentials do not match error is because the auth method tries to do a hash match on your input, but as the password is in plain text in the database it will fail.