Cumulative Using Summarized Table

Hi,  HugoJesus 

Try to modify the formula as below:

...
.....
VAR LastDay =
    MAX ( Date_Link[Calendar] )
VAR TempTable2 =
    ADDCOLUMNS (
        TempTable,
        "Open_Tickets",
        var _date = [Calendar]
        return
            SUMX(
                FILTER(
                    TempTable,
                    [Calendar]<=_date
                ),
                [Daily_Open_Tickets]
            )
    )
RETURN
    TempTable2

The result will show as below:

Please check the attached pbix file for more details.

Best Regards,
Community Support Team _ Eason
If this post helps, then please consider Accept it as the solution to help the other members find it more quickly.