I inserted the following formula into cell C39:

=SUMPRODUCT(--(D3C3),--(F3E3),--(H3G3),--(J3I3),--(L3K3),--(N3M3),--(P3O3),--(R3Q3),--(T3S3),--(V3U3),--(X3W3),--(Z3Y3),--(AB3AA3),--(AD3AC3),--(AF3AE3),--(AH3AG3),--(AI3AJ3),--(AL3AK3),--(AN3AM3),--(AP3AO3),--(AR3AQ3),--(AT3AS3),--(AV3AU3),--(AX3AW3),--(AZ3AY3),--(BB3BA3),--(BD3BC3),--(BF3BE3),--(BH3BG3),--(BJ3BI3),--(BL3BK3),--(BN3BM3))

When I enter numbers into cells in the formula cell C39 still displays "0"

Any tips?