If you are having troubles logging in, it could be one of many causes. So here is what you need to do in order to get to the root of the problem.
1. Make sure you're not mixing GitHub login with email+password
Make sure that you actually have an account with the email+password. Often times, we see users who've previously authenticated with GitHub trying to login with the email+password. This will not work. If you signed up with GitHub, you have to login with GitHub as well (even though you might use the same email address on GitHub that you're trying to login with at Scrimba).
2. Try to clear the cookies in your browser
We've had issues where users have had two Scrimba login cookies in their browser. This might cause you to not being able to login. In order to fix this, please clear the cookies Scrimba.com has added to your browser. Here is an article which explains how to do exactly that: