Seeded HR Reports not returning any results

Summary: Hi , We actually have to run all the seeded HR reports and present the output to the client . Now I got the list of the seeded reports but when I am trying to run these , I am not getting any output for most of them even though data is present in the system. From security side , I checked , I have all the required roles and privileges. But some of these reports are returning results and some are not.

Content (required): The Department and Assignment reports aren't returning any result despite data being present in the system. What could be the reason for this? Along with this do we have any document or reference available on the seeded reports?