Cannot access pages after logging in.

Info:
WordPress v4.0
iThemes Security v4.4.20
DesignThemes Deam Spa v 1.1

Issue:
I have used iThemes Security to edit the admin login page, and I get a message “You have logged in successfully.” <- however the page does not redirect, and whenever I try to go to any of the admin pages I get redirected to my error 404 page.

Temporary fix:
I have resolved the issue by disabling the plugin (renamed the folder), but would really like to be able to use it for security.

Any ideas?

https://ww.wp.xz.cn/plugins/better-wp-security/