ASP.Net Error: 40 - Could not open a connection to SQL Server

A network-related or instance-specific error occurred while establishing a connection to SQL Server. The server was not found or was not accessible. Verify that the instance name is correct and that SQL Server is configured to allow remote connections. (provider: Named Pipes Provider, error: 40 - Could not open a connection to SQL Server)

 

I have checked the connection between the both servers.

 

Database is accessed for other webserver.

 

No issues with connection strings, user name & passwords.