Ran into this error earlier today while trying to install WSUS using a remote SQL 2014 SP2 server with non-standard SQL ports.
2016-11-22 20:30:13 Stopping service WSUSService
2016-11-22 20:30:13 Stopping service W3SVC
2016-11-22 20:30:13 Configuring database…
2016-11-22 20:30:13 Configuring the database…
2016-11-22 20:30:13 Establishing DB connection…
2016-11-22 20:31:14 System.Data.SqlClient.SqlException (0x80131904): 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) —> System.ComponentModel.Win32Exception (0x80004005): Access is denied
at System.Data.SqlClient.SqlInternalConnection.OnError(SqlException exception, Boolean breakConnection, Action`1 wrapCloseInAction)
at System.Data.SqlClient.TdsParser.ThrowExceptionAndWarning(TdsParserStateObject stateObj, Boolean callerHasConnectionLock, Boolean asyncClose)
at System.Data.SqlClient.TdsParser.Connect(ServerInfo serverInfo, SqlInternalConnectionTds connHandler, Boolean ignoreSniOpenTimeout, Int64 timerExpire, Boolean encrypt, Boolean trustServerCert, Boolean integratedSecurity, Boolean withFailover)
After a little troubleshooting it turned out the SQL Browser service on the SQL server was stopped. Starting the service and running wsus setup again fixed it.
