Formula result will not show when formula is copied to another cell

I had created this formula that worked fine:
=INDEX('COGS sorted '!$F$9:$F$249,MATCH(A47,IF('COGS sorted '!$B$9:$B$249=C47,'COGS sorted '!$A$9:$A$249),0))

I then added an ISNA formula to the above formula in cell L43 and the result is blank but should be 529.39. This is the formula:
IF(ISNA(INDEX('COGS sorted '!$F$10:$F$250,MATCH(A43,IF('COGS sorted '!$B$10:$B$250=C43,'COGS sorted '!$A$10:$A$250),0))),"",INDEX('COGS sorted '!$F$10:$F$250,MATCH(A43,IF('COGS sorted '!$B$10:$B$250=C43,'COGS sorted '!$A$10:$A$250),0)))

I know that Excel won't display a result if the formula contains over 255 characers, but my formula has only 236. Anybody know why the result is not being displayed?

Thanks!