Technical Blog Post
Don't forget about that Front End Server property!
One of the most important properties that is easily overlooked is the Front End Server property. This property must be set for BIRT reports to render correctly on the application server. If you have a process server, the URL value of the Front End Server property on the application server and the process server must be the application server. It is also important to set this property for queued reports, since the generated URL is composed from this property. You can set this property during the installation process or in the TRIRIGAWEB.properties file, which requires a restart before it takes effect. The following example shows the property and its description from a 3.4.1 installation.
# The FRONT_END_SERVER is the main URL an end user would enter to access
# the IBM TRIRIGA system. It consists of a protocol(optional),
# host[REQUIRED] and port (optional). If no protocol is specified
# then "http" will be used by default.