First, please check that you are on the correct URL. Way too often users try to login on a wrong domain which then obviously doesn't work ;-) Correct URL should be this one:
Second, please check the error message. If it says "Sorry, wrong e-mail or password" you are trying with a wrong password or your email is not registered in our system. In that case please try to reset your password (use the Forgotten password form).
If even the password reset doesn't work, then most likely your account doesn't exist in our system. Please reach out to your account manager or Raphael Cohen (firstname.lastname@example.org).