I have 5 projects in my workspace.
All 5 have similarly setup iterations, stories, features, and releases.
One of them just doesn't work in release tracking burnup chart. It hows one of the iterations with weird spacings in the text, and a large grey box in the middle. No stories or anything. The grid shows lots of features by iterations with story counts correct.
Iterations all line up with each other. release timebox is correct. Stories all have features and iterations.
I have created a support case for you. The Support Team will work with you via that case on this issue.