I upgraded ArcGIS 11 from 10.9.1. Ugrade successfully completed after that reauthorised new license for 11 is done. I am getting Site can't reached error while loading http://localhost:6080/arcgis/manager/
You may want to look at this patch: https://support.esri.com/en/Products/Enterprise/arcgis-server/ArcGIS-Server/11#downloads?id=8084
"After installing or upgrading to ArcGIS Server 11.0, you must apply this patch before proceeding with the Create Site or Continue Server Upgrade process."