"Uploag-in" will make a file input at your login page. You can upload the key file to login. It makes your login security more powerful.
If that user is not an administrator, login with administrator account and go to User. See that users profile and generate new key or delete key.
If user is administrator, connect your mySQL and delete row named sj-uploagin-key of user_id is 1. (delete from wp_usermeta where user_id=”1″ and meta_key=”sj-uploagin-key”)
It is impossible to login via iPhone. I will fix that problem in next version.