Deadlyduck,

with SUMPRODUCT you'd normally do double unary or multiplication, but not both, so

=sumproduct(--(P104:p170=a135)*(S104:s170))
should either be

=sumproduct((P104:p170=a135)*(S104:s170))

or

=sumproduct(--(P104:p170=a135),(S104:s170))