Rally Iteration Burndown (Core app) is showing data as blank

Products

• Rally SaaS

Issue/Introduction

The Core App Iteration Burndown has stopped working for one of my Teams (project).

I have deleted and re-added the app 2 times with no change. The app comes up but no data is shown. 

Cause

The Iteration in Rally that the Team was currently working had been updated to Accepted. The iteration was changed  back to Planning and the Iteration Burndown now shows data.

Resolution

Change the affected Iteration from Accepted to another state and the Iteration Burndown will shows data.