I too have suffered the nightmare that is JPA reporting. It is a sad sign of the times that we are using PPrune to disseminate information on how to use this software! It took us ages just to be able to access the reporting system through JPA.
For what it's worth - another top tip is ensuring you have 'Jinitiator' installed on your machine otherwise nothing happens when you click on any of the reporting links from the JPA home page!