Verify that the instance name is correct, and that SQL Server is configured to allow remote connections. (provider:named Pipes provider, error:40-Unable to open connection to SQL Server)

Program exception, error message: A network-related or instance-specific error occurred while establishing a connection to SQL Server. The server was not found or could not be accessed. Verify that the instance name is correct, and that SQL Server is configured to allow remote connections. (provider:named Pipes provider, error:40-Unable to open connection to SQL Server)

I also have this problem today, solved, first make sure your MSSQLSERVER built-in account is: Local System, if not on the SQL Server Configuration Manager--sql Server service, locate SQL Server (MSSQLSERVER) Start or modify the built-in account as: Local System restart. You can do it.

Verify that the instance name is correct, and that SQL Server is configured to allow remote connections. (provider:named Pipes provider, error:40-Unable to open connection to SQL Server)