Your issue is that your dimensions are Date as first dimension and Product Group as second dimension, while you probably want to aggregate your values by Date per Product Group (i.e. Product Group as first dimension, Date as second). It only works in your pivot table because you pivoted Product Group to the top.
When comparing a table to a line chart, you need to look at a straight table chart, which shows the same problem, right?
To get around this issue (showing your data in a different dimension order than when calculating the rangesum()), you can use advanced aggregation:
=
aggr(
RangeSum(Above( Sum(ReplenishmentVolume),0,rowno()))
-
RangeSum(Above(Sum( {<SalesDatum={">$(=(Date(Today()-92,'YYYY-MM-DD'))) "}>} HistoricSalesVolym) / 90,0,rowno()))
+
RangeSum(Above( Sum(StockVolume),0,rowno()))
,P_Varugruppnr, P_Date)
Note the different dimension order. I assume you want to reset the rangesum for each product group, so you need to remove the total qualifier again. I also replaced the 99 with rowno(), but not sure if 99 is a special requirement for you (running total for last 99 values?).
Last, to make this work, you need Date dimension values load order to be sorted chronological (because aggr() function sorts its dimension values only by load order).
This is not the case yet in your document!
You need to create your date field values in a chronological order first, before loading in your facts.
After you've done that, your chart should work as expected.
