Does not appear to find the string values, "Go,Stop"....they are in the
file.
Does the ISNUMBER expect a numeric value or can it be a string?
There could be extraneous white leading/trailing spaces in col B's data
throwing some apparent matches off. Try it with a TRIM to enhance matching,
viz.:
=SUMPRODUCT((A1:A6="Y")*(ISNUMBER(MATCH(TRIM(B1:B6),{"Go","Stop"},0)))*C1:C6)
ISNUMBER merely converts the matched array retuned into an array of
TRUEs/FALSEs, depending on whether the elements are numeric or non-numeric