After upgrading, a GIS administrator tries to log in to Portal for ArcGIS using admin...

After an upgrade, Portal for ArcGIS often changes web elements, scripts, and cached content. If the browser is using old cached files, the portal page may not render correctly, and authentication may fail. Clearing the browser cache ensures that new files are loaded.

From Esri documentation:

“After upgrading ArcGIS Enterprise, clear the browser’s cache to ensure that all updated components and scripts are loaded properly.”

Option A is a diagnostic tool, not a fix.

Option B may be excessive if the issue is simply browser cache.

Option D is not a standard troubleshooting step.