Invetory reduction function not working

[Svlab]

Hello

I have copied the Order Capture App and adjusted some basic features, but then I noticed that the Invetory reduction function is not working. when I add the product the numbers on the data doesn’t change or reduce any quantity
I checked everything is as default on the Order capture but not working only works when I reduce it manualy from edit in the table of the app for products.
Please help