A burndown report will only report information related to your work items' estimate. A Story work item does not normally have an assigned estimate. You would not see any information related to your plan in the burndown report if there isn't any estimate information. You can either add work items to your plan as child work items that do contain some estimate, or assign some estimate to your stories. By default, the editors for your Story work items do not have any estimate presentations, but if you want, you can add a presentation to allow your users to set this attribute's value.

I believe that you would get more information in the progress report, if you are using story points and not estimates. You can read more information on how your plan's reports work by looking at http://www.ibm.com/support/knowledgecenter/SSYMRC_6.0.1/com.ibm.team.apt.doc/topics/c_review_progress_web.html