When exporting a dashboard as PDF it worked fine but when scheduling the same dashboard it produced a blank PDF with only the text "The specified dashboard wasn't found" in it.
There were no errors generated in the jasperserver log file but noticed the key difference is the time it takes from the entry 'New Session Created' to the entry 'About to shutdown'.
[INFO - 2018-09-12T05:09:26.397Z] SessionManagerReqHand - _postNewSessionCommand - New Session Created: 05157e90-b64a-11e8-9d46-fdf46e4ed099 [INFO - 2018-09-12T05:12:05.219Z] ShutdownReqHand - _handle - About to shutdown
It was found that there was a misconfiguration in the file js.config.properties (located under ../jasperserver-pro/WEB-INF) where the property deploy.base.local.url was set to an address that was blocked by a web application firewall.
It is necessary set the property as follows and restart the TIBCO JasperReports® server:
or if going through HTTPS: