When ArcGIS Pro 1.1 is licensed with Portal for ArcGIS's Named User license, users are unable to update to ArcGIS Pro 1.2 using the software update with the error, "The Esri Update service is temporarily unavailable" even though the user is signed in to ArcGIS Online and set it at the active portal.
Duplicate of BUG-000097834: Issue addressed in ArcGIS Pro 1.3.0.
対処法
Perform a manual update of ArcGIS Pro 1.2 by uninstalling ArcGIS Pro 1.1 and installing ArcGIS Pro 1.2. This issue is not reproducible with ArcGIS Pro 1.3.