Have you logged in using a different method before? Perhaps with Google?
If so, the problem is most likely that the authentication system I'm using is being picky about which method you log in with. Try a different method to see if it works.
I know from experience that if you, for example, sign in with Github under [email protected] and then tomorrow log in with Google with the same [email protected] address, you will now only be able to log in with Google.
If, on the other hand, you are trying to log in with username/email and you forgot your password, go to the sign-in form, and click "Forgot my password" under the inputs.
Still having trouble? Send me an email