In an order, VendHQ only recognizes product IDs instead of SKUs. So, when BigCommerce order data comes through to VendHQ, it's technically unable to update inventory levels.
Our solution is to create a list of your SKUs and Product IDs on our system, and then we can put in a function that will transform the data from one to another. So when BigCommerce order data comes in, we transform the SKU to the Product ID before sending it to VendHQ, thus ensuring that VendHQ reads the data and updates the inventory levels.
The only thing we require from you is to let us know whenever new products have been added so that we can add their SKUs and Product IDs onto our system. Otherwise VendHQ will not be able to update its inventory if someone orders these new items on BigCommerce.