Working with thousands of instances of Microsoft SQL Server, I often encounter users having issues. A common error is 18456 which indicates a login failure. Some common solutions are listed below.
- Incorrect Credentials
- Usually this is related to a password issue or incorrectly entering username/password. Verifying how the user is trying to connect and further looking into the error log can provide more details.
- Authentication Mode Mismatch
- This is very common in organizations that use SQL Authentication in addition to Windows/Entra/etc. I’ll usually ask the end user to send me a screenshot of the screen they are entering their credentials to confirm they are using the correct mode.
- Account is Disabled or Locked out
- With having password policies in place, it is very common to have expired passwords, or locked accounts due to someone trying old passwords too many times.
- Permissions Issues
- This is typically worked out fairly quickly after an account is created, however someone may have either not asked for the correct permissions up front, or a step may have been missed when the account was created. Common situations are not granting the ‘connect’ permission.
- Default Database Issues
- Not selected a proper default database or not granting proper permissions to the default database. You can usually find these errors in the SQL Error Log.
- Check that SQL Server Service is running
- I’ve often found this error and found that SQL Server Service was not running. Starting the SQL Server Service back up resolved this issue.
When you encounter this error, pay attention to the “State Code” in the error message. This will give you more details into the failure to aid in your troubleshooting.
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