Stacked Bar Charts - Why can I only see totals in Dashboard?

Hi, probably a really easy question, but it's got me flummoxed.

I've inherited a portfolio of around 90 projects and I'm trying to build some Dashboards.

I have the required data in a Report (a snippet)

yet the "Stacked Data" still displays as a solid block.

I feel like I'm missing something completely obvious - is it to do with the fact that Status is in the Primary column?