In O5, try this:

=SUMPRODUCT(('Pivot FCST'!$A$5:$A$695=$B5)*('Pivot FCST'!$B$5:$B$695=$C5)*('Pivot FCST'!$C$5:$C$695=$D5)*('Pivot FCST'!$D$5:$D$695=$E5)*('Pivot FCST'!$E$1:$V$1=O$2)*('Pivot FCST'!$E$2:$V$2=$D$1)*('Pivot FCST'!$E$5:$V$695))

Note that the calculations are set to manual in the workbook that you shared.