Hello
Did you already try to run MRP on MD03? Do you see a planned order created?
Check on transaction MD21 if the planning file entry is created for this material. If it is not, you should run transaction MDRE to make sure that all the planning entries are created.
Also, try to run MRP on transactioN MD43 and check if there is any error message or check for errors on MD05.
BR
Caetano