User is trying to run the Billing Forecast report in Core, but it is always blank.
This happens if you do not have a billing schedule set on any of your projects. This report compares the amounts that are scheduled to be billed on projects with the amounts that are actually billed. So if you do not use Billing Schedules on any projects, the report is going to have no data on it. Check the Core Help for more on Billing Schedules.