=IFERROR(VLOOKUP(B5,AC$2:$AQ$76,5,FALSE),NA) is wrong
that needs to be
=IFERROR(VLOOKUP(B5,AC$2:$AQ$76,5,FALSE),"NA") or =IFERROR(VLOOKUP(B5,AC$2:$AQ$76,5,FALSE),NA())