Make sure that the ASP. NET State Service (ASP) is started and the client port is the same as the server port

Exception Details: System.Web.HttpException: Unable to issue a session state request to the session-state server. Make sure that you have started the ASP.
Service, and the client and server ports are the same. If the server is on a remote computer, check
Hkey_local_machine\system\currentcontrolset\services\aspnet_state\parameters\allowremoteconnection
value to ensure that the server accepts remote requests.
This is because an unhandled exception was generated during the execution of the current WEB request because the ASP. NET State Service is not open.

Workaround:
Method One:

Right-click "My Computer"-"Computer Management"-"services and Applications"-"services", locate the ASP. NET Status service in the service, start ASP.
State Service, it's ready.
Method Two:

The mode of configuration sessionstate in Web. config is stateserver, but the server specified does not have the service open.
Can be changed to InProc.

<sessionstate
Mode= "InProc"

Stateconnectionstring= "tcpip=127.0.0.1:42424"
sqlconnectionstring= "Data
Source=127.0.0.1;user id=sa;password= "
Cookieless= "false"
Timeout= "20"

/>
You are not using "stateserver", if yes, please refer to:
Using StateServer mode
Ensure that the ASP.
The state service is running on a remote server that stores session-state information. The service is installed with ASP. NET Premium, and the service is located by default in
<drive>:\program Files\asp.net\premium\version\aspnet_estate.exe.

In the application's Web. config file, set mode=stateserver and set the stateConnectionString property, for example
Stateconnectionstring= "tcpip=sarath:42424".
Method Three:

May be on the machine antivirus software in mischief, think is a virus, do not allow page loading, the anti-virus software off.

Make sure that the ASP. NET State Service (ASP) is started and the client port is the same as the server port