Double check your email and password. Make sure you are using the right email address and password.

Is your caps lock on? Check that your "caps lock" button is not on! Indeed the password is case sensitive, upper and lower case letters make a difference

Reset your password. If the above two options do not work for you and you have forgotten your password, you can always reset your password by clicking on the "Forgot Password" button. An email will be sent to you with more instructions on how to make a new password.