You are trying to use the internal Sales Order Integration EDI in a B2B scenario.
Reproducing the Issue
You cannot find any information on Slaes Order Integration in the Service Explorer.
The B2B web service SalesOrderProcessingOrderingIn with access URL <hostname>/sap/bc/srt/scs/sap/salesorderprocessingorderingi1 is not visible in the Service Explorer, because the web service only released for usage in context of integration scenario Sales Order Integration.
The B2B inbound interface SalesOrderProcessingOrderingIn with access URL <hostname>/sap/bc/srt/scs/sap/salesorderprocessingorderingi1 is the interface of choice for B2B ordering scenarios. You get the interface by creating a communication arrangement for communication scenario “Sales Order Integration”. We currently have no plans to deprecate or replace this interface.
You can create sales orders via Web Service API or via B2B inbound interface; explained in this blog post https://blogs.sap.com/2017/08/10/create-byd-sales-orders-using-web-services/.
A detailed description to configure the B2B service: Setup B2B Sales Order Integration with SAP Business ByDesign.
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