If you have no Inventory defined, or you do but have not made any Inventory Purchases, or if you have done both but have no Recipes defined, there is no way it will be able to figure out anything regarding Inventory, never-mind Cost.
How do you expect Inventory Reports to show anything when you have not defined Inventory Items, or even if you have, if you have not made a Purchase, or even if you have, you have not configured Recipes, so the system knows how much something costs.
It does no good to tell us that something does not work, without showing details. A blank Report Screen is not details of anything. I might as well be staring at a blank black chalkboard and you tell me nothing is there. No shit.
EDIT: sorry for my rant, but we cannot help you if you don't help us.
Show screenshots of:
- Inventory Item(s) that you have set up
- Recipes that you have set up showing Inventory Items that comprise a Menu Item Product
- an Inventory Purchase Transaction
- a sale of a Product
- the Inventory and Cost tabs of the Warehouses Screen