I think we figured out why we were experiencing problems with the advanced burndown report not displaying the bars for remaining story points:
The report which showed the problem is configured with a fairly large number of iterations (50+). Based on Allana's post above and based on the observation that the problem surfaced around the point in time when we changed the current iteration, we decided to create smaller report configurations to better understand what happens if only past iterations are selected, if past iterations up to the current iteration are selected and similar configurations with future iterations.
Interestingly, when we tried to execute the report configured with a few past iterations up to the current iteration, the chart did not show the bars, but the report also displayed the following error message:
"ERROR: This report can only generate a burndown chart for a single release, but you have selected multiple iterations that have project release plans defined (R1, I42). Please re-run the report and choose a single release together with all its child iterations."
R1 is the top-level iteration for the current release, I42 however is the current iteration.
With this information, we checked what plans had been created for the current iteration, and as it turned out, one of the component teams used plan type "release backlog" for their I42 plan, where they probably should have selected sprint backlog instead. After changing the plan type and running the warehouse ETL jobs, both the "small" report worked as expected (especially was showing the bars for remaining story points), as well as the "large" configuration with all 50+ iterations selected. We hope that this was the only cause for the bars to disappear!
With this problem hopefully understood and fixed, I have two open questions remaining:
1) Why was the error message only shown on the "small" configuration, but not on the large one?
2) What is the relation between advanced release burndown and plans of type release backlog? The implications of this relationship should be mentioned in the documentation, I think.
Thanks,
Markus