SAP Message 61139 - Requirements planning is not active in plant &

Diagnosis
The basic requirement for carrying out the planning run is that MRP hasbeen activated via customizing for the plant for which you want to runthe planning program.

Procedure
Aktivate MRP via customizing for MRP by choosingActivate MRP and set up planning file.
If you do not have the necessary authorization to do this, notify yoursystem administrator.