Step is not allowed for non-oil materials

What causes this issue?

The material master has not been correctly maintained. The material is
defined with a conversion group at another plant and no conversion group
has been entered for the plant.

System Response

The conversion group activates the Quantity Conversion Interface (QCI).
It is not possible to define a material with a conversion group at one
plant and omit it for the same material at another plant. It is possible
to utilize different conversion groups for each plant.

How to fix this error?

Maintain the current material with a valid conversion group and unit of
measure group.

Error message extract from SAP system. Copyright SAP SE.