Calendar Express is no longer installed automatically in a fresh install. If you are performing a fresh install of Calendar Server 6.3, but want to use Calendar Express as your user interface, you must explicitly install it using the Communications Suite 5 installation program. Then you must configure it by adding service.http.ui.enable="y" to the ics.conf file. (The default internal setting is "n" for fresh installs, so you must explicitly set it to "y".)
If you are upgrading from an earlier version of Calendar Server, the upgrade process adds the parameter to the ics.conf for you, with the value set to "y". This allows the legacy user interface to continue to be used without any changes. However, if you wish to disable it, set this parameter to "n".