Running rowcount with filter by date

Try this one :

RunningTotalFileUploaded = 
VAR CurrentDate = MAX(Activity[Date Created])
VAR FilteredTable = 
    FILTER(
        ALL(Activity[Date Created]),
        Activity[Date Created] <= CurrentDate
    )
RETURN
CALCULATE(
    COUNTROWS(Activity),
    FilteredTable,
    Activity[Operation] = "FileUploaded"
)

If above measure still not workable, then try the summarize version given below. First will summarize the activity table by date created and operation and count and then do cummulative sum:

RunningTotalFileUploaded = 
VAR CurrentDate = MAX(Activity[Date Created])

VAR SummaryTable = 
SUMMARIZE(
    FILTER(
        ALL(Activity),
        Activity[Operation] = "FileUploaded"
    ),
    Activity[Date Created],
    Activity[Operation],
    "Count", COUNTROWS(Activity)
)

RETURN
SUMX(
    FILTER(
        SummaryTable,
        [Date Created] <= CurrentDate
    ),
    [Count]
)

Hope this helps!!

If this solved your problem, please accept it as a solution and a kudos!!

Best Regards,
Shahariar Hafiz