I can't sign up the system.

I am not sure if I have understood your question correctly. You already have an account with your email address, why do you want to sign up again.

Do you mean to say that you are not able to sign in to your JotForm account? I would suggest you to please click on the following URL to sign in to your JotForm account: https://www.jotform.com/login/

Do try it out and get back to us if you have any trouble.

We will wait for your response.