Diagnosis
You want to create a class item with resulting item category &V2& for aconfigurable BOM with BOM usage &V1&.
Settings in Customizing (Bills of material) control which items can beentered for each BOM usage.
For BOM usage &V1&, class items with resulting item category &V2& arenot supported.

Procedure
Choose a BOM usage which supports class items with resulting itemcategory &V2&.
If you really want to enter a class item with this resulting itemcategory, consult the person responsible for bills of material. It maybe possible to make a change to the BOM usage or the item category.