SUMIFS not working

Dear Members, i am not getting my SUMIFS to work correctly.
refer the attachment.
One sheet i maintain the inventory (Whatever comes in)
Second sheet i maintain the invoices (Whatever goes out)
I want to track how much been sold and how much been left in the Inventory sheet lively.
I am sure SUMIFS should work, but i am wrong somewhere!

Please help.

Regards
Krish.