Diagnosis
There are two possibilities in this case:

• either you have already started the planning run for the plant and this
is being carried out at present

• or the planning run is still locked due to a blocking entry from the
previous planning run.

Procedure
In the second case, you must unlock the planning run. You do this asdescribed below:
Make sure that no planning run is active as if a planning run is activewhen you try to unlock MRP, this could lead to incorrect results.
Select Tools -> Administration
Select Monitoring -> Lock entries