This behavior is actually by design. Pie charts can’t have both multiple series and category items and thus requiring both is not right.
Now, for pie and gauge charts, we only require a series dimension and everything else is a filter.
Your pie charts from older versions get upgraded so that:
the category dimension gets moved to series
everything else becomes a filter
NB: Please note that this does not affect the visual presentation of your existing pie charts, they will look the same and show the same data. We just make sure that the chart layout for pie and gauge charts is no longer misleading.
Thank you Jan for the information. The reason I raised this was because we were getting this with all our previously created pie charts if you opened them in the new visualizer