SAP Message /ISDFPS/FORCER040 - MPO &1 is not assigned to the force element

Diagnosis
Equipment package &2 contains a material of MPO &1 as the mainor required material. However, this MPO is not assigned to theforce element. This means that the equipment package cannot beassigned either.

System Response
The system rejects the assignment.

Procedure
First assign MPO &1 to the force element.