There are many installation scenarios that can cause TRIRIGA reports, especially BIRT reports, to fail to export due to timeout. Microsoft Excel exports are often the ones that you can observe because all of the file formatting happens during export.
Let’s focus on WebSphere Liberty installations, but this recommendation can be used for other web servers with some tweaks. Mostly, this is related to timeout settings, especially for HTTPS (SSL/TLS) connections. A good troubleshooting test is to perform the same action in a non-HTTPS (HTTP) connection. Does the report export? If so, take note of the time needed to export it and plan to extend the timeout in the HTTPS connection to at least double the time.
Refer to the IBM Knowledge Center > WebSphere Liberty > HTTP Endpoint topic. Look for the “sslOptions”, and also double-check the “httpOptions”, for timeouts.