SOLVED! License Activation (Slui.exe) Failed

If your attempt to activate Windows ends in failure and your only lead is an entry about “License Activation (SLUI.exe) failed…” in Event Viewer, the usual suspects include VPN, firewall and connection. In terms of solutions, you could activate Windows manually, make use of SLUI, disable basic authentication, … Spare some time to take a look at this article to activate Windows and put it to good use.

What Might Have Gone Wrong


Generally speaking, VPN (Virtual Private Network) comes in handy for those that care about privacy while connecting to the Internet. That being said, VPN is well-known for complicating a couple of processes on Windows computers and product activation is a prime example. Hence, regarding activation difficulty and Event Viewer logging “License Activation (SLUI.exe) failed…”, you should give VPN some thought. 


For your information, a firewall keeps Windows computers out of harm’s way but it may create problems as well. If the firewall suspects activities to be malicious, it will block them regardless of their true nature. Needless to say, the activation of Windows would hit a wall if the firewall flags it by mistake. On the bright side, if the firewall is at fault, there is no need to do much. 


The activation of Windows only proceeds smoothly if there is a stable connection to the Internet. In the case that your Internet connection is less than ideal, it’s only natural for the process to fail. Do you keep seeing the “License Activation (SLUI.exe) failed…” entry in Event Viewer? Then you may want to take your connection into account. 

How To Address The Issue

Activate Windows Manually

  • Step 1: Go to Search bar, type cmd and click Run as administrator on the right side to open Command Prompt with administrator privileges.

  • Step 2: In  Command Prompt (Admin), run the command: slmgr /ato. Wait for a moment and if things proceed smoothly, you should see a Windows Script Host prompt saying Product activated successfully.

  • Step 3: Click OK, close Command Prompt and restart your computer. When the screen comes back, you should see an entry about “Acquisition of End User License was successful” in Event Viewer. 

Take Advantage Of SLUI 

  • Step 1: Go to Search bar, type SLUI and hit Enter. 

  • Step 2: Click on the Best match option to open the wizard. 

  • Step 3: If your OS is not activated, click on Activate and enter your product key once asked.

  • Step 4: Click Next and follow the instructions.
  • Step 5: Restart your computer.

Activate Windows Via Phone

  • Step 1: Go to Search bar, type slui 4 and click Run as administrator on the right side. If slui.exe 4 displays the Activation Settings page, it means your Windows is already active thanks to a digital license.

  • Step 2: Select your country and press Next. Windows will provide you with some toll-free numbers you can call.
  • Step 3: Dial any of the numbers on your phone. When the call connects, provide the operator with the installation ID you see on the screen (second line).

  • Step 4: On their part, the operator will give you an ID. Click on Enter confirmation ID and enter the given ID.
  • Step 5: Press Activate to initiate the process.

Disable Basic Authentication

  • Step 1:  Go to Search bar, type windows features and click Turn Windows features on and off.
  • Step 2: Proceed to find Internet Information Services and click

  • Step 3: Select World Wide Web Service and choose Security.
  • Step 4: Under Security, uncheck the checkbox next to Basic authentication.

What is License Activation (SLUI.exe)?

Also known as the Windows Activation Client, SLUI.exe is a system process that helps in activating Windows licenses. Each PC needs a license that allows the user to use the premium features. Microsoft allows a user to take advantage of the Windows OS, but only for a limited period. After that, SLUI.exe takes over and reminds you that you’re using an unactivated version of the OS.

Where is SLUI.exe?

Legitimate slui.exe resides in C:\\Windows\System32. If you see slui.exe in other locations, it may be malware. 

What Happens If I Don’t Activate Windows?

Windows may still work if you don’t activate it. However, unless you activate Windows, there is no way for you to access all the features. 

How Long Can Windows Be Used Without Activation?

30 days.

Can I Activate Windows For Free Legally?

No. Windows is proprietary software, meaning that you can’t use it for free legally. All places that tell otherwise are likely asking you to use a pirated version.


  • Sometimes, “License Activation (SLUI.exe) failed…” is harmless and people could carry on using their computer. The entry is the result of the automation registration service trying to verify whether your product key is valid.
  • Avoid using fake online product keys to activate your Windows version. Instead, buy a legitimate version of the OS from Microsoft’s website. Although you may pay upwards of $200 for a product like Windows 10 Pro, you will own an authentic copy and could access support.

  • If $200 is too much to spend on an OS, visit other platforms like to get deals that are over 50% to 80% low.

  • Microsoft Windows Key Management Service is now able to know if your OS copy is pirated. Actually, recent updates allow Windows Security to detect key-hosting registry files and block them as it does with viruses.
  • Stay away from sites that promise to help you activate your Windows for a small fee. Such platforms don’t last long because Microsoft is always looking for ways to block pirated software from accessing premium Windows features.

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