This will typically happen when the item is assigned to a department that is either marked as exclude from shipping or not defined at all. To check this perform the following:
1) Login to ProductControl
2) Open RealtimeCompliance
3) Go to File|Configuration|Department Shipping tab
4) Click Load RMS Departments
5) Mark the departments as either Ship or Exclude in the Action column
Any department that is marked as Ship should also have a product type defined.
From there you will need to check the item's properties in Store Operations Manager to ensure the item is associated with a department that is marked as Ship.