Admin pages not looking or working right
There are three main things that we’ve seen cause this:
The theme you’re using may be causing trouble and you can test this simply changing to the default theme for a moment and reloading the admin page you’re having trouble with.
Some plugins have also been known to conflict in a way that may cause the s2Member admin pages to not work correctly.
To test these, just deactivate them all and reload the page, or deactivate them one by one and check after each if the problem is gone.
Try changing back to the default index.php file and reload the admin page.
If the above don’t solve the problem, there are a couple more things you could try. Please see this article: Troubleshooting Tips