Panel not working after installation

I installed freepbx following the instructions on this web site, all works well. I create extensions, trunk, they are fine.
But when I click Panel on the web page, I see this information on the screen, "internet explorer canot display the webpage, most likele causes, you are not connected to the internet, the web site is encountering problems…"
I guess some service is not running on the server or some access right is not set correctly, any one has some idea ?