I have updated my ArcGIS Server from10.5.1 to 10.8.1 and after upgrade the essential services, such as CachingTools, PublishingTools, and ReportingTools are in stopped state and not able to start these services. Getting the error "System.ReportingTools.GPServer: java.rmi.UnmarshalException: Error unmarshaling return header; nested exception is: java.net.SocketException: Connection reset". ArcGIS Server machine has been updated from 10.5.1 to 10.8.1. This server is not part of enterprise deployment. This is an individual single server deployment.
I Have gone through couple of knowledge base articles and verified HKEY_LOCAL_MACHINE\SOFTWARE\Python\PythonCore\2.7\PythonPath at the location and it exists properly. Also I Ran "Configur ArcGIS Server Account" tool to make sure that ArcGIS Service account has all the required privileges. I also tried repair ArcGIS Server but no luck. Any help will be much appreciated.