Error: Cannot Open Server Requested by the Login. The Login Failed.

Issue

Destination connections fail with the following error:

Cannot open server "<IP address>" requested by the login. The login failed.

Environment

Connector: SQL Server (Azure SQL Database or Azure SQL Managed Instance)

Resolution

To resolve this issue, update the username in your Azure SQL connector configuration:

1. In Fivetran, go to your SQL Server connection page.
2. Select the Settings tab.
3. Click Edit connection.
4. In the User field, enter your username in the format username@<server_name>.
   Replace <server_name> with the server name only. Do not use the full FQDN. For example, if your server FQDN is myazuresqlserver.database.windows.net, enter fivetran_user@myazuresqlserver.

5. Click Save & Test.

Cause

This issue occurs when the Azure SQL instance uses a Private Endpoint. When this happens, Azure SQL requires the username to include the server name in the username@<server_name> format for authentication and routing. Connections fail when you use only the username, the full FQDN, or an incorrectly formatted username.