Unable to login to SQL Server + SQL Server Authentication + Error: 18456

The detailed error message and stack trace you’ve provided indicate a login failure for the ‘sa’ user in SQL Server. The error number 18456 and severity 14 generally point to issues related to authentication or permissions. Here’s a more detailed troubleshooting approach based on the provided information:

1. Verify SQL Server Authentication Mode

Ensure that SQL Server is configured to allow SQL Server Authentication (not just Windows Authentication).

1. Open SQL Server Management Studio (SSMS) and connect using Windows Authentication.
2. Right-click on the server instance (UMESH-PC\SQLEXPRESS) in Object Explorer and select “Properties”.
3. Navigate to the “Security” page.
4. Verify that “SQL Server and Windows Authentication mode” is selected. If it is not, select it, and restart the SQL Server service.

2. Check the ‘sa’ Account Status

Confirm that the ‘sa’ account is enabled and that you have the correct password.

1. In SSMS, connect using Windows Authentication.
2. Expand “Security” -> “Logins”.
3. Right-click on ‘sa’ and select “Properties”.
4. Under the “Status” tab, make sure “Login” is set to “Enabled”.
5. If you suspect the password might be incorrect, you can reset it here.