There is a stored query that returns a list of tickets. When the list is sorted by certain fields (like Assignee for instance), the list of tickets disappears as if there were no results from the query. When it is sorted by another field (Open Date for instance), then the list will reappear, and it also shows if you click on the scoreboard node again.
The list is being shown using the wrong form for the ticket type. Service Desk will default to list_cr.htmpl, but this will cause issues when showing types of tickets other than Requests.
You need to modify the query to include a type constraint similar to this:
The above constraint will limit the results to just Incidents, and that will also tell Service Desk to use the right form for the list. For other ticket types, use the proper tag - P for Problems, or R for requests.