delivery not possible

I try to create a delivery based on sales order, but hit below error:

No schedule lines due for delivery up to the selected date

Message no. VL248

Diagnosis

There are no schedule lines due for the given order item up to the date chosen.

System Response

The system does not create a delivery item for this order item.

Procedure

Check whether the order item to be delivered contains confirmed schedule lines.

If this is the case, set the selection date further into the future if you still want to create a delivery for this item.

how to resolve the issue?