During setup using the Provisioning Services Configuration Wizard, connecting to a Microsoft SQL Express instance installed on another machine fails with the error “Invalid Server”.

The specific error code is either “error: 26” or “error: 28”;
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: SQL Network Interfaces, error: 26 – Error Locating Server/Instance Specified)”

“A network-related or instance-specific error occurred while establishing a connection to SQL Server. The server was not found or was not accessïble. Verify that the instance name is correct and that SQL Server is configured to allow remote connections. (provider: SQL Network Interfaces, error: 28 - Server doesn't support requested protocol)”

Complete the following steps on the computer with Microsoft SQL Express installed:

1. Open SQL Server Configuration Manager.

2. Set the SQL Server Browser service to Automatic.

3. Start the SQL Server Browser.

4. Ensure the Named Pipes protocol is enabled.

Problem Cause

By default, installing Microsoft SQL Express does not start the SQL Server Browser service (referred to by error: 26), and does not enable the Named Pipes protocol (referred to by error: 28).
If both causes are present, error: 26 appears.