how are you opening it? when you open report objects in regular mode (report view), it prints automatically I believe, doesn't it? this is not true though, for print preview mode.
do you have any screenshots of the report opened up inside the app and the subrpt being visible, and then one of it missing in the printout?
Welcome. FYI I moved your thread out of the introductions forum.
Report view is the not the same as normal view which prints automatically. Different events fire for those views so I'd see if there's any code running. Also, report view doesn't paginate like print view, so it may be the section you have it in.