Named Pipes connections cause failure to SQL Server
This article helps you to resolve a consistent authentication issue that causes a Named Pipes connections failure to SQL Server.
Symptoms
The SQL OLE DB provider displays the "SQL Server does not exist or access denied" error message.
Some other providers display both the following messages in a random order, whether you use integrated security or a Microsoft SQL Server login:
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.
Could not open a connection to SQL Server.
Some other providers might additionally display "Login timeout expired" within the error message.
Cause
The Named Pipes connections fail because user doesn't have permission to log in to Windows.
Resolution
Add the user to the Users group on the server that's running SQL Server. If SQL Server is mirrored or clustered, repeat on all computers within the group.