This feature is available in Enterprise and Ultimate editions
I moved quite a few backlog items from an original project to a subproject underneath the original one. When I view my release burndown chart for the subproject it has no data. Why?
Reports such as the burndown present a historically accurate representation of the data. The burndown data is displayed in a project only for the period in which the project held the items.
In this case, the items existed in a different project in the past so their burndown up to this point is reflected in the prior project. Now that they have been moved into a new project, their current status will be reflected in the burndown of this project going forward. The Burndown graph that applies to the Project/Release level is the Estimate Burndown, which shows the amount of remaining (Open) Estimate. The Burndown graph that applies to the sprint level is the To Do Burndown, which shows the amount of remaining To Do in that sprint. The overall historical accuracy rule stated above applies to both these burndown graphs.
Line graphs require two data points to be able to draw a line; no line will be displayed until values for two periods exist (days, weeks, etc. depending on the report parameters). Data will show up sooner if you select a smaller duration for your report.