cumulative sum

Hi,

I am not sure how your semantic model looks like, but I tried to create a sample pbix file like below.

Please check the below picture and the attached pbix file.

Sales: = 
SUM(sales[sales])

WINDOW function (DAX) - DAX | Microsoft Learn

Cumulative sales: = 
CALCULATE (
    [Sales:],
    WINDOW (
        1,
        ABS,
        0,
        REL,
        ALL ( 'calendar'[Year], 'calendar'[Month name], 'calendar'[Month number] ),
        ORDERBY ( 'calendar'[Month number], ASC ),
        ,
        PARTITIONBY ( 'calendar'[Year] )
    )
)