There are several potential reasons:
1) no orders match your query.
2) the filter field you have selected is case sensitive. Try change the case. This is a know issue and we are working to make all field non-case sensitive.
3) the most likely issue is that you must change your date range. There are no matching orders for the date range you have selected.
You can specify a date range to restrict the listing content on the dashboard, in the Discover list, any of the workflow queue lists. The default date range is the past 7 days, though you can change it to the last 24 hours, last 30 days, last 90 days, or any specific date range that you find necessary.
The current date range appears in the top-right corner, such as "Last 7 days".