This feature is available in Enterprise and Ultimate editions.
New to Reports?
Refer to the Reports article to learn more.
The system uses the history of items to plot the burndowns and other trend graphs. To see a burndown line, there must be enough data in the system for at least two data points. If you are looking at a daily duration, you will see a burndown line beginning on the 2nd day. If you are looking at a weekly duration, typically, that means you will see a weekly burndown on the 8th day. If you change the start date so that the end of a week falls somewhere in the middle of your data, it is possible that results display on the graph with less than seven full days worth of data.
There are two possible causes:
Data has not yet accumulated
Your dates are off
How to Fix It
Give it time
Line graphs, such as the burndown, require two data points to actually display a line. If you just got started and entered all this information on the same day, you will be able to see your burndown line the next day.
Check the dates
Your entered data may fall outside the date range of the graph. The burndown shows the date range defined for the sprint itself, so if your sprint hasn't actually started yet or was in the past and data is just being entered now, the data will not display.
Note: The current data point for a single day is actually plotted on the graph and the details can be viewed by hovering your mouse over the point if you happen to know where it is, but it is not represented visually until that 2nd data point appears.