Scenario:
When you run a report that is created based on the Project Status report, you may not find some projects in the report data, despite having the Approval Status filter set to Approved, Rejected, Waiting and Open.
Hierarchy filtering is enabled and the projects that do not show up are visible even to the root department of the company. The projects are open and time entry is allowed.

Resolution:
By default, if there are no time entries made by any user against projects, then those projects wont show up in this report. In other words, no user associated with the project has entered any time against it. If you still want to report on Projects that have no time entries made, then edit the this report Settings to disable Approval Status from the Filters tab and enable the Task Time Entry Status filter.