issue in assigning delivering plant see the message

Hi I have issue while creating sales order and entering the delivering plant . I am getting the following message,

I made the plant assignment in customer master etc., still showing the same message.

what is that required now?

message is:

Enter a valid delivering plant

Message no. V1755

Diagnosis

The customer for the delivering plant is the same as the sold-to party.

System Response

The system cannot determine a valid delivering plant.

Procedure

Check if a delivering plant has been entered in the customer master, material master, or in the customer-info record, with identical

customer and sold-to party.