Extensions not showing

Because of Extensions page uses Joomla!'s pagination and filtration the pagination and filtration made in other places (e.g. Articles) will effect Extensions page too.
For example if you've been viewing the second page of your Articles then if you go to AceSEF Extensions page you wont find any extension if you dont have too much extensions installed.

To fix this, reset the Filter, if the issue persist then go to a page that has more than 1 pages and go to page 1. Then go back to Extensions page.