Hi,
That does not look like a web dynpro for ABAP app. It seems to be a Java app. It uses RFC to communicate with ABAP backend. The RFC connection fails for some reason. So you can use ST01 to trace RFC calls or authorization checks. Probably, it is a missing authorization for S_RFC for function group that is used by that screen. It could be something else. For example the RFC call dumps.
Cheers