Lookup returning #N/A

Good morning again, Gurus.

In the attached workbook, cell C31, I have a lookup formula to find the action code for a part in the Vendor NPA worksheet. The lookup works for the first part number in the NPA, (NI1225162C), but returns an #N/A for the 2nd part number, (FO1225173C). The formula is unchanged. I can't use vlookup because the action code is to the left of the lookup criteria.

Any ideas as to why I'm getting the not found error?

Thanks in advance.