First of all, you should be convinced, that your server uses the
mod_status module. For this purpose open in your text editor a web
server configuration file httpd.conf. Find the section loading modules
and check up, whether there is there a line:
LoadModule status_module modules/mod_status.so
This line can differ a little depending on the version of your server
and operation system. If this line has ahead a symbol # that remove
it.
Read more at
http://www.hs-lab.com/usage/faq/content/2/1/en/how-to-configure-apache-versions-13x-_-20x-.html