If an invoice cannot be created because the message comes:
(Pas de données supérieures/ Dati superiori non esistenti!/ Bewerkte bestanden niet voorhanden!/ Brak dokumentu nadrzędnego!)
it is usually because an information was not filled correctly during the representative determination.
In this case, please open the order and go to the tab "Miscellaneous" in the header view. Here delete the line of the representative and insert it again.
Save the order and create the invoice again.