I fixed it by attaching the specific report to the menu bar. The behavior setting of the report: "Generate on load", must be set on True. The reportpane is now a startpage for all users.
What do you exactly mean by "automatically generating a report pane"?
You can define a report pane and place it on the start page. Since 2.4.3 you can also define a microflow as startpage to show a user or user role specific startpage.