Inventory not Updating

[BearNecessities]

Hi there, i recently created a simple inventory management app that tracks stock in and out of a warehouse. I used this formula on a virtual column in the inventory data sheet 

SUM(
SELECT(
INVENTORY[QTY IN STOCK],
[PRODUCT BARCODE] = [_THISROW].[PRODUCT BARCODE]
)) +
SUM(
SELECT(
Restock[QUANTITY],
[PRODUCT BARCODE] = [_THISROW].[PRODUCT BARCODE]
)) -
SUM(
SELECT(
Stock Out[QUANTITY],
[PRODUCT BARCODE] = [_THISROW].[PRODUCT BARCODE]
))

The Stock Out and Restock Sheets update their columns as expected however the QTY IN STOCK value does not change. 

please advise as to what i have done wrong.

[BearNecessities]

I see my issue is not that the virtual column is not getting the correct value it is, however how do i make it update the sheet.