School single sign-on
For many users, their college or university email address and password are used to sign in. Such users would be redirected to their school's login portal upon selecting the Log In button.
If you are unable to log in through your school's login portal, contact their IT support directly; there is an issue with your account on the school side.
Philo Edu account
Users that do not sign in through their school's login portal require a specific Philo Edu account. Such users would have received a welcome email containing their login credentials and setup instructions. (If you are unable to locate this email, it may have ended up in your spam or junk folder - please check there.)