10001009 
Message
Item [number of item] is not a purchasing item
Diagnosis
You have tried to create a purchasing document for an item containing a child item that is not specified as a purchasing item (the option Purchase Item in 
Inventory 
Item Master Data General
Area 
is not selected).
You have opened the purchasing document, specified a vendor, and on the Contents tab, from the Item No. column, you have opened the List of Items window.
The option Purchase Item in the Item Master Data record of the specific child item was deselected.
You have chosen the parent item from the List of Items window.
Procedure
You can create purchasing documents only for items that are specified as purchasing items.
Recommendation
If it has been a while since you have opened the List of Items window until you have actually chosen the item, close the List of Items window and open it again to refresh the display. If the status of an item has been changed, and it is no longer a purchasing item, this item does not appear in the refreshed list.