My Epic Burndown chart only shows the last Sprint completed

[Jeff Abbott]

I created a board to track requirements implemented.  Software sprints were already complete. I needed to walk the requirements through sprints to see how they were burning down across sprints.:

1. My estimation method is Issue Counts. 
2. I added all requirements to my Epic
3. I created my sprints but did not start them.
4. I used bulk update to assign issues in bulk to my sprints.
5. At this point I have one bar on my Epic Burndown showing all requirements in Blue as Work Remaining. 
6. One sprint at a time, I started the sprint, moved the issues to a Done state and closed the sprints using the past dates of the SW Sprints (dates before the this board was created).
7. Each time I close a sprint it is the only bar displayed. There are two categories of issues (Work Completed and Work Added). 

I am at a loss as to why the earlier sprints are not on the burndown, and why there is no Work remaining even through there are requirements still in the Epic in the To Do state.