How come VLOOKUP only works till the third row?

I have attached a simple spreadsheet with two tables: one that has a list of categorized items, and one that defines certain attributes for each category.  I am using VLOOKUP to copy the category attributes from Table 2 into Table 1.  However, I am not having much luck with this seemingly simple endeavor.

In the sample file, there are five categories, each with a two-letter identifier.  On the items table (the one on the left), the first three categories (ED, FI, and PO) all have the correct modifier associated with them.  However, the fourth category (HE) pulls the value from the FI category, and items with the fifth category (AB) get a "Value Not Available" error!

How come VLOOKUP is not behaving as I would expect it to?
VLOOKUP-Example.xlsx