We are trying to script some automation for publishing sde services from Pro 2.5 to our Portal site. I've been able to create the .sd draft but when trying to StageService I get error 999999. Anyone else run into this issue?
Does this link cover your error?
https://community.esri.com/thread/247963-arcgis-pro-25-fails-to-overwrite-web-layer-staging-failed