Hi,
just to be sure: You specify the user for the Activities from the SharePoint Integration Pack with Orchestrator Runbook Designer, click Options, and then click Microsoft SharePoint. The creds from SharePoint Configuration there do not need to be the same as the Logon Account for Orchestrator Runbook Service (for me: "Orchestrator service account").
Which version of the System Center Integration Pack for Microsoft SharePoint do yo use? This is the newest for SC 2019: [https://www.microsoft.com/en-us/download/details.aspx?id=58111&WT.mc_id=rss_alldownloads_all
Regards,
Stefan