The site is configured with a login page which displays the Account Login module. The administrator cannot edit this page, but an alternate page can be checked and set as  default login page.
In order to restore the primary login page you need to access the site settings, by checking the option “Site settings”  in the Menu or click the icon . Click Advanced settings and Page management.

If any page is checked (‘<None Specified >’) the default Login Page will be used.