Hi Jean-François,
Thank you for the question. The button that you are clicking in the Sales Order is intended to allow you to navigate to a Purchase Order which is already linked. Since you do not have the line linked to a Purchase Order, you have the error returned.
In order to create and link the Purchase Order, you must open the Purchase Order page. The help page which contains instructions can be found here: [View:https://madeira.microsoft.com/en-us/documentation/sales-how-drop-shipment/:750:50].
Also, the specific instructions are here:
To create the purchase order for drop shipment
To prepare a drop shipment for the item to be sold, you create a purchase order as normal, except you must indicate on the purchase order that it must be shipped to your customer, not to yourself.
- Create a purchase order. Do not fill any fields on the lines. For more information, see How to: Record Purchases.
- In the Sell-to Customer No. field, select the customer that you are selling to.
- Choose the Drop Shipments action, and then choose the Get Sales Order action.
- In the Sales List window, select the sales order that you prepared in the "To create a sales order for drop shipment" section.
- Choose the OK button.
The line information from the sales order is inserted on the purchase order line(s).
You can now instruct the vendor to ship the items to your customer, for example, by mailing the purchase order as a PDF.
I hope that this information helps. Please respond if you have further questions on this topic.
