In Communications panel, select Manage EventStream (Actions menu on the right - the icon is a paper plane inside a speech bubble)
Under the Settings tab, there are three options: Leader Boards, Automated Posts, and Moderate.
Under “Leader Boards”, select which items you want to appear, and tailor the headings if you want to.
Since Leader Boards are a kind of automated post, Leader Boards will only work if the dates for Automated Posts are set up properly (start and end dates for Automated Posts must be no more than 1 day outside of your event dates).
If you're having problems, try making adjustments to your Automated Posts dates, then:
Check if the Leader Board appears in the Attendee App.
If the Leader Board is still not displaying correctly, confirm all date changes were saved and retry.