Only individual planning possible (no quantity-based inventory mngt.)

What causes this issue?

For every possible combination of material type and plant you can
define whether quantity-based inventory management is allowed or not.
This is done in Customizing. If it is not allowed, the material may
only carry the "Individual requirements" indicator.

System Response

Quantity-based inventory management is not allowed for the material
type and plant of the current material.

How to fix this error?

Enter the "Individual requirements" indicator for this material.

Error message extract from SAP system. Copyright SAP SE.