The SAP Business One Connector tool is configured to update the Sales Order or Purchase Order object, and the DocEntry is mapped to make it find the correct Order. However, when you add new lines it updates the existing lines instead of adding new ones
The default behaviour for the connector tool is to update existing lines using the relevant line number. Therefore default behaviour does not allow for adding new lines.
You need to pass -1 as the linenum so that the tools know that you want to add lines.
BPA Platform for SAP Business One
BPA Platform is a SAP Certified integration solution for SAP Business One. BPA Platform supports the central creation and management of an Integration Platform as a Service (iPaaS).
It is designed specifically for SAP channel partners and customers who wish to connect SAP databases to third-party solutions and accelerate the automation of business processes.
Deploy BPA Platform in a Cloud, Hybrid or On-premises environment and get the integration and process automation tools you need when you need it.