BOM Quantity Calculations

Hi Experts i created FMS to sum up the quantites of BOM Row level to show on Header Level my FMS is

SELECT sum(T1.Quantity) FROM ITT1 T1 WHERE T1.Father =$[$3.2.11]

but its showing zero instead of Quantitiy sum

Can any one guide me what am i missing in this FMS

Regards

Jamil