How do I get the inventory counts for items to update when they are received in the Purchase Order module?

I recently joined a company using Sage 300, and I've been trying to get their system working. In the past, they used generic item numbers on purchase orders (i.e. BATHHARDWARE1), so their inventory counts were useless because many items shared the same item number. I have implemented unique item numbers, and I thought that would solve the inventory problems. However, it seems that even with unique item numbers, the Receipt Entry in the Purchase Order module is not updating item inventory counts in the Inventory Control module. What could be causing this?

I know that I can go into the IC module and update these inventory accounts manually, but that is obviously an incredibly wasteful workflow. Should Receipt Entry be able to make these updates in inventory, or do I need to use another transaction process to get that to happen?