I have played around with the provided model file and and added an additional chart (Matrix 1 – Pie (2D) – new). Just take a look at this chart.
I don’t know why it works when you drag the categroy B onto the right and the category A onto the top – but it does! Check the attached file below.
I have another question:
How can I drag the value lables out of the pie slices for better readability?