Choose a lot size for which the lot-sizing procedure "lot-for-lot order quantity" is defined.

I need help in resolving following concern

I am facing an error when trying to extend MRP1 view in a new plant to the already existing material (which is of type FERT)

I am trying MRP Type PD, Lot Sizing Procedure FX, Lot size 50

Error i am getting is :

Enter a valid lot size (materials planning) Choose a lot size for which the lot-sizing procedure "lot-for-lot order quantity" is defined.

I have already done the configuration for material type FERT enabling it to be quantity managed in OMS2.

Yet the error is not resolved.

Any help would be highly appreciated