Scheduled Reports are always empty

Summary: I created a few different 'Scheduled Reports'. I receive the report by email as expected, and the report has column headers, but NO DATA.

I am new to creating scheduled reports so maybe I am missing a step in the setup?

Content (required): I created several different reports from Dashboards 'Scheduled Reports'. The report is received by email as expected, and the report has column headers, but there is NO DATA. For example I created a report "Average Travel Time per Resource" and selected "first_day_of_week" as the start date, and "today" as the end date. I received the report with column headers but there is no data inside the report.