The 301 link wasn’t just a URL. It was a logic redirect —like an HTTP 301 redirect—pointing from a dead-end error to a living workaround. The page said: “Your ArcGIS Pro instance is trying to authenticate via an old portal URL. Create a new portal connection file and repoint the project.”
Could you clarify if you are looking for a for a specific version or troubleshooting a URL redirect error in ArcGIS? esri arcgis pro 301 link