SD Bill of Materials (BoM) Explosion

Hie All.

I created a header material (800000-0001) under MM01 with Item Category NORM. Later on I created my BoM using transaction CS01 where I attached several materials. When I enter the header material (800000-0001) during Sales Order creation (VA01), it doesn't explode to show the materials I attached to the BoM. Even if i try to do outbound delivery I get the error message: Document does not contain selectable items. What's really the problem?

Regards,

Joseph.