Message SAP WXP051 - Some quantity key figures are not ready for input

Diagnosis
Quantity key figures can only be maintained in planning if units ofmeasure have been maintained in the planning hierarchy for thecorresponding characteristics combination.

Procedure
If you want to maintain quantity key figures at the current planninglevel, you have to define units of measure in the planning hierarchy.This only makes sense if the units of measure are clearly defined atthis planning level.