As per the config here https://meta.wikimedia.org/wiki/Config:Dashiki:WMCSEdits, for the hierarchical view in T226663, we show the last 60 months' data.
In a scenario, where the difference between the last two date outputs is more than 60, the pie chart goes missing. Currently, the last time the data generated was for January and outputted as 2020-01-01, so clearly, it has been more than 60 days since. As the new data now get generated every month on the 4th, maybe when the ReportUpdater generates the data for February and outputs it as 2020-02-01 (which might be anytime soon), this view will be functional again. Not sure what the workaround would be here. Maybe change showLastDays for the hierarchical view to 90 in the config?
