Diagnosis
Categories have not been assigned to all the shops in the articlehierarchy.

System Response
If the "Multiple Material Assignment" flag is set, the system checkswhether a category has been assigned to the article hierarchy for allexisting and affected shops. In a distribution chain-dependenthierarchy, the shops of the active distribution chain are checked.
If categories have not been maintained for all shps, you cannot activatethe article hierarchy.

Procedure
Maintain the category assignment for the shops without a category.
Maintain Shop Category Assignments