How do I fix the “Failed to connect to the KMS server” error?

Windows 10 prompts users to install the latest updates on their device, but sometimes the server fails to connect to the Internet. This seems more annoying when the problem is undetectable. After installing MS Office on your device, your work is interrupted due to a KMS server disconnection error.

Sometimes after installing MS Office on Windows 10, there is a KMS server failure problem. There are two main reasons for this problem:

  • The client computer does not respond
  • Internet connection problem or connection interruption.

Sometimes when you install Office on a Windows computer, your work is interrupted because the connection to the KMS server fails. Here are some solutions in case this happens.


What causes the “Failed to connect to the KMS server” error

What causes the "Failed to connect to the KMS server" error

There are two main reasons for this problem

  • The reason is the client: first of all, make sure that Windows update is enabled and that your Internet connection is stable. To check if the KMS servers are blocked or not, please open your Internet browser and try to access the page. If the page is visible, it means that this server is not blocked. Another point to pay attention to is that you must run the prompt/batch file with administrator rights. Otherwise, the connection will be interrupted by the UAC system.
  • Server reason: we had to do some experiments with the kms7 server recently, so we changed the default KMS port (1688) to a different one. We also upgraded the processor and RAM of the kms8 server. With too many daily clients, which increases over time, the server can sometimes crash. You can check on their website to see if the server is overloaded or not. To check if port 1688 is open, you can use the telnet command in Windows


How to fix the “Failed to connect to the KMS server” error

How to fix the "Failed to connect to the KMS server" error

Check your Internet connection
  1. Open the Start menu.
  2. Type cmd.
  3. Double-click “Command Prompt.”
  4. In the command line window, type ping -n 25 and press Enter.

Sometimes the error is only displayed because your Internet connection is not working. If everything looks good, you can proceed to the next steps.

Update your Windows operating system

Often problems with KMS server functionality occur when the Windows operating system is not properly licensed. By having an original license, not only can you be sure that your product is legal, fully functional, and reliable, but you also receive regular updates that help prevent errors from occurring.

In addition, upgrading to the latest version of Windows is a one-time expense, so your investment will pay off in the long run.

Make sure that your computer is activated
  1. On your KMS client, open the Control Panel.
  2. Look for the “Windows enabled” message.

If it is not activated, you will need to activate it first and then activate your copy of Office. Before you activate your copy of Office, we need to make sure that Windows is enabled on the client computer.

Check if you have more than 25 clients
  1. Open a command prompt window as an administrator.
  2. Run the slmgr.VBS /dli command to see if the threshold is reached. Currently, the threshold is 5 for server editions and 25 for all others.
Verify that the client has contacted the host

On the host KMS computer, look for event ID 12290 in the application event log. Check this log for requests from the client computer. If there are no requests, it means that the client could not communicate with the host.

Open the right port
  1. As an administrator, run the command line.
  2. In the cmd window, type the command slmgr.vb /dlv.
  3. Search for sniffing on the port.

Make sure that no firewall rules are blocking TCP traffic on the KMS port. The default value for the port is 1688. If you do not know the port, you can find it on the host computer.

Configure DNS correctly for multiple KMS hosts
  1. Make sure that all computers are in the same Active Directory domain of domain services.
  2. Create a global security group in the Active Directory Domain Services domain.
  3. Add each computer running KMS to the newly created global security group.
  4. Set permissions to allow updates by members of this new group on the DNS server.

When using KMS, the host computer must be discovered on your local network. The first host computer automatically announces its existence when the SRV record is created on the DNS server. Other hosts cannot change or update the SRV record if the DNS server is not properly configured.

Newly added hosts do not increase the number of KMS
  1. On the client computer, open the search bar.
  2. Type cmd.
  3. Right-click the command line and select Run as administrator.
  4. In the command line window, type Sysprep /generalize to reset the client computer ID. If that doesn’t work, try slmgr / weapons.

Sometimes client computers appear to be identical to the host and are not counted separately.


Frequently Asked Questions

  1. Right-click the Start menu and select Command Prompt (Admin).
  2. Run the slmgr command from a script.
  3. Run the slmgr command by script.
  4. Finally, run the cscript slmgr.

Activations on the KMS server expire after 30 days, so over time the number of activations on the server drops below 25 and computers can no longer be activated.

The Key Management Service (KMS) is unavailable. This may be due to the fact that the client is configured to a specific KMS server, which may not be available. To solve this problem, you must run the "Remove KMS Saved Server" application in the CCIT Application Catalog or run the following two commands from the administrative line.

  1. Log on to the computer with an administrator account.
  2. Type cmd.exe in the search box.
  3. Right-click on cmd.exe and select "Run as administrator".
  4. Press 'Enter'.
  5. Type to complete the activation process.

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Mark Ginter is a tech blogger with a passion for all things gadgets and gizmos. A self-proclaimed "geek", Mark has been blogging about technology for over 15 years. His blog,, covers a wide range of topics including new product releases, industry news, and tips and tricks for getting the most out of your devices. If you're looking for someone who can keep you up-to-date with all the latest tech news and developments, then be sure to follow him over at Microsoft.