Please suggest configuration in following scenario:

(1) eCommerce company is : E-company

(2) Stock is in ERP company : P-Company

(3) Stock is maintain by Serial number in company P-Company

(4) Portal user will place order from E-company while actual stock is in P-Company

(5) essential Product template configuration :

General Information -> Product Type ->Storable product

ecommerce - > Availability -> Show inventory on website

and prevent sales if not enough stock

inventory -> By Unique Serial Number

inventory -> Routes -> Replenish on Order (MTO)

Currently, with above configuration, the Portal user can't place order.

Please suggest a viable configuration

Thanking you.