Admin pages with query string redirect to the frontpage
If you are trying to visit "Click to view your system’s configuration in a new window" and end up on the frontpage of your website instead of the system information page, your theme may be using the template_redirect hook incorrectly.
WordPress has a built in function called template_redirect which allows Theme authors to make redirects that are informed about the specific state of WordPress during a request. For example, it can be used to make different redirects depending on whether a user is logged in or not. On occasion, authors will use the template_redirect hook in a way that breaks all URLs that request the root of the site and have query strings, because it redirects all those requests to the website frontpage.
There is unfortunately no fix for this, other than to ask the theme developer to change how their code works so it doesn't impact other URLs on the website. You can read more about the template_redirect hook and how to use it in the WordPress documentation. Please note that as the docs state, loading a different template is not a good use of this action hook.