DAX Month Cummulative using SUMX RANKX

Hello

I am trying to work out the cumulative amounts for each month using the following dax queries with Rankx.

Month Numbers = 
SWITCH([Total Sales Ranking by Month],
"JAN", 1,
"FEB", 2,
"MAR", 3,
"APR", 4,
"MAY", 5,
"JUN", 6,
"JUL", 7,
"AUG", 8,
"SEP", 9,
"OCT", 10,
"NOV", 11,
"DEC", 12,0)

Cumulative Sales by Month Number = 
var monthNos = [Month Numbers]
RETURN
SUMX(
    FILTER(
        SUMMARIZE(
            'Calendar', 'Calendar'[Month],
            "Sales", [Total Sales],
            "Sales Ranking", RANKX(ALL('Calendar'[Month]), [Total Sales], , ASC)
        ),
        [Sales Ranking] >= monthNos
    ),
    [Sales]
)

But I end up with the same values in both the Total Sales and Cumulative columns. What am I doing wrong? 

Thanks

Yoshi