Hello,

Please see my response:

1) Create Business Unit and make sure you enable Business Unit Business Functions "Material Management"
2) Create Item Organization and assign Business Unit (ex: ABC Business Unit)
3) Create Inventory Organization and assign Item organization , which you have created in Step 2 and assign same Business Unit that you have assigned to Item Master ( Ex: ABC Business Unit)
4) Assign Roles - Product Manager & Product Data Steward
5) Run Role Synchronization program
5) Navigate to Item Class and query Root Item Class and make sure you assign your Item Organization and Inventory Organization under Security by selecting Roles (product manager) and under actions , select all options.
6) Create Item , you should see both Item Org and Inventory Org.

In case if the issue still , please do send me screenshots.