The most common reason for not being able to change your password is that you originally created your account with Google or Facebook and now you are trying to login with an email and password. In this case, Google or Facebook manages the authentication so changing your password in Stagehand will not work.
Please try to log in with Google or Facebook. If that still doesn't work, send us a note.
If you didn't sign up using Google or Facebook or you did not receive the email that allows you to reset your password, check your Junk/Spam folder.