How to Fix Login Failed Microsoft SQL Server Error: 18456

Wondering how to fix Login Failed Microsoft Server error 18456?

The Microsoft SQL Server is a database management program that manages data from numerous software programs. It has an important position and a high demand in the digital world but unfortunately, it is not entirely immune to logical mistakes.

Recently, several users reported that they have been encountering the SQL Server Error 18456 upon their attempt to log in using SQL authentication. If you are facing a similar issue, you are in the right place because in this guide, we will walk you through several methods of fixing the issue in detail.

Let’s get right into it!

1. Launch the SQL Server as Administrator and Disable UAC on the Server

If you haven’t provided the SQL server with elevated permissions, it might not be able to execute its operations properly, resulting in the error at hand. You can fix this issue by launching the SQL server as an administrator and disabling UAC on the server.

Open the SQL Server as Administrator

  1. Type SQL Server Management Studio in the search bar and click on Run as administrator.
  2. If your screen displays User Account Prompt, click on Yes to proceed and check if doing so resolves the issues.

Launch the SQL Server in a Single User Mode

  1. Type SQL Server Management Studio in the search bar and click Open.
  2. Right-click on the SQL Server service in the right pane and select Properties from the list of options available.
  3. Now go to the Startup Parameters tab and in the Specify a Startup Parameter box, type the following.
  1. Click Apply to save the changes.
  2. Next, right-click on the SQL Server service and select Restart.
  3. Once done, type SQL Server Management Studio in the search bar and right-click on SMSS.
  4. Select Run as administrator and check if you can connect to the SQL Server as administrator.
  5. If you can, add the domain account to the SQL server and assign it the SysAdmin role.
  6. Then, go back to the SQL Server Configuration Manager window and delete the -m parameter from Start-up Parameters.

Finally, restart the SQL Server service using the method we discussed above and check if it is working correctly.

2. Enable the TCP/IP Protocol in the Server Configuration Manager

SQL server error code 18456 indicates that the connection could not be authenticated, and this occurs when the TCP/IP protocol required to access a database over a network is disabled by the Server Configuration Manager. In this situation, enabling TCP/IP through SQL Server Configuration Manager could solve the issue.

  1. Open Windows and click on Microsoft SQL Server with a year listed along it. For instance, 2010.
  2. You can now open SQL Server Configuration Manager and click Yes (if you were prompted by UAC).
  3. Next, expand SQL Server Network Configuration, and then select Protocols for (the database/server name) on the left side of the window.
  4. Now, in the right pane, double-click on TCP/IP and select Yes in the dropdown menu against Enabled.
Microsoft Server error 18456
  1. Then apply your changes and head over to the search area of your taskbar.
  2. Now type Services and select Run as Administrator.
  3. Right-click on the SQL Server (with the server’s name) and then select Restart.

The SQL server should now be free of the error 18456.

3. Change the Authentication Mode of the SQL Server

When the authentication method of the SQL server is not properly configured, the server might display error 18456. It might be possible to resolve this problem by changing the authentication method of the SQL server. If you intend to move forward, make sure the status login is enabled for the user.

  1. Right-click on your server and choose Properties in the Object Explorer of Microsoft SQL Server Management Studio.
  2. Now, select Security in the left pane. In the right pane, choose SQL Server and Windows Authentication.
Microsoft Server error 18456
  1. Next, apply your changes and right-click the server in the Object Explorer.
  2. Select Restart and after restarting, verify that you can access the database without Error 18456.
  3. If you cannot log into SQL, then you may install MS Power Tools.
  4. Once done, run the following in an elevated command:
psexec.exe -i -s ssms.exe

You can then make the changes by using the installation account for SQL and also make sure the SA account isn’t disabled.

4. Try Using CleanMyPC.

You might encounter problems executing the methods to fix the error under consideration if your operating system contains corruption errors.

Generally, corruption issues are caused by junk files in your system, so if you haven’t cleaned them up recently, now is the time. Our team recently tested some of the most popular cleaners available and CleanMyPC came out on top. 

Install CleanMyPC on your PC

The program includes a variety of tools for system maintenance that can do much more than just remove junk files. Multi-Uninstaller, Registry Cleaner, and a Speed Booster are among the tools it comes with. To fix the problem, install CleanMyPC and run a scan through it. Any issues found will be handled automatically without much user interaction.

Install CleanMyPC now and get your PC up and running like new!

 Try CleanMyPC Now!

5. Create a New Login and Restart the Reporting Services

If you cannot log in to the reporting services, then creating a new login and restarting the reporting services might help you fix the issue. 

  1. Open the Microsoft SQL Server Management Studio and expand the Security tab.
  2. Then expand Logins and right-click on it.
  3. Now click on New Login and enter the credentials

Note: Select the computer account in the login name.

  1. Ensure that “User Must Change Password at Next Login” is unchecked, and then select the database.
  2. Now go to the Server Roles tab and select Public role.
  3. On the User Mapping tab, select db_owner from the list of database owners.
  4. Now apply your changes and head over to the search area of your taskbar.
  5. Type Services in there and then select Run as Administrator.
  6. Locate and right-click on the SQL Server Reporting Service. Then select Restart.

Finally, reconnect to the database and check if the SQL server is clear of the error 18456.

This brings us to the end of our guide on fixing Microsoft Server error 18456. We tried walking you through all the steps in detail and hope that one of the methods mentioned in this post did the trick for you. In case you still have any confusion about the troubleshooting steps, please let us know in the comment section below!

If this guide helped you, please share it. 🙂


  • Zainab Falak

    Zainab Falak is a staff writer for Saint and an expert in Microsoft Windows, having authored more than 200 posts. She has a Bachelors in Actuarial Sciences and her passion for computers extends to exploring various aspects, from UI customization to the Windows registry and exploring error codes. Twitter LinkedIn

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