Vlook Up function not working Properly, donot know, need help

still not working

see attached the file, there are 2 tabs
Sheet 4 Column C has VLook up formula
to pulling the cost from sheet 5 column D

I think I have the correct formula, and some item does not have cost, but some do, vlook up at least pull the cost the item has cost

don't know why its not doing it

can you please help, that what's wrong with my formula

thanks again