If you are importing items that have a vendor, but no item code CG-XL may not import the vendor.
The work around is to enter a receipt, choose Show All Items. Choose the items you want, a pop up asking for item code will appear. You can cancel out of that.
Once you have all the items for that vendor you can CANCEL out of the receipt without saving it. And you will see the vendor associated with the item in Inventory Manager