Unable to connect to SQL Server

este es mi error :

System.Data.SqlClient.SqlException HResult=0x80131904 Message=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) Source=.Net SqlClient Data Provider StackTrace:

Inner Exception 1: Win32Exception: The network path was not found

I already confirmed username and string and they are fine, what I am doing is a simple web services to consume data from sql server, but this error comes out, and everything is fine in sql server, this is my enter image description here