I've installed ISPConfig, created a Site and after that installed and configured Munin to work with the newly created site. Then I configured that in ISPConfig > System > Server Config > mydomain.com > Munin URL > http://www.mydomain.com/munin
So, if I access www.mydomain.com/munin
it shows the monitoring graphs. Nice.
But, if I go to ISPConfig > Monitoring > Show Munin, the ISPConfig panel shows just a line stating "Munin (Server : www.mydomain.com)" and a blank area.
I'm using ISPConfig 188.8.131.52 in CentOS 6.5, both up-to-date.