If you had a previous Method account and want to sign up for a new Method account and use the same sign in email, you will have to use the same password as before. For example, you created a Method account with the sign in email of firstname.lastname@example.org with password thisismypassword. If you want to create a new Method account and use email@example.com again, you will have to enter the same password as before, thisismypassword on the sign up screen.
If you don't remember what the password was, you can reset the password for the email. When you successfully reset the password, you may get a message saying "No Accounts Found" but don't worry and go forth with signing up with a new account using the sign in email and the password you just set.