Some Office users are reporting that they are encountering the ERR_MISSING_PARTNUMBER error code after inserting a valid license key in order to activate their Office product. In most cases, this problem occurs after affected users performed a clean install or reinstalled the Office suite.

Error Code ERR_Missing_PartNumber

As it turns out, there are multiple scenarios that might contribute to the apparition of the ERR_MISSING_PARTNUMBER issue:

  • Outage with the Office for the webserver – You might end up seeing this error code due to an Office activation server problem that’s widespread. If this scenario is applicable, the issue is entirely out of your control. All you can do is pinpoint the problem and wait for Microsoft to fix the problem on their side before you will be able to activate your Office suite.
  • The incorrect product key or activation service – This is confusing for a lot of Office users, but not all product keys can be activated via Office.com/setup. Depending on your Office edition, you will have to download & activate it via different links. In this case, follow Method 2 for steps on determining whether you’re using the correct license key and how to activate it.
  • User tries to activate volume license key via Office.com/setup – In case you’re using a volume key for an Office Professional Plus edition, you need to enforce the activation either via MAK (Multiple Activation Key) or KMS (Key Management Service).
  • User tries to activate a One-Time Purchase license – it’s also possible that the reason you’re seeing this error is that you’re trying to activate a license that can only be installed on your computer and Microsoft rejects. In this case, you will need to get in contact with a Microsoft Live agent and ask them to activate the license remotely.

Method 1: Verifying the Office Service Health

Before we troubleshoot this issue thoroughly, your first step should be to confirm that the problem is not widespread and is only occurring for you.

It’s possible that the reason you are unable to activate your Office suite is due to a server issue that Microsoft is currently dealing with. In situations like this, the issue is entirely beyond your control – All you can do is confirm that the problem is occurring and wait for Microsoft to fix the issue on their side.

To check for any problems that might affect Office, visit this link (here) and see if Microsoft is currently reporting any problems associated with Office (Office for the web -Consumer).

Verifying the status of the Office Servers

If your investigation shows no issues with the Office server, you’ve just confirmed that you’re not dealing with a server issue. In this case, move down to the methods below for additional steps of fixing the issue if it’s occurring locally.

Method 2: Ensuring that you’re inserting the correct product key

If you get the ERR_MISSING_PARTNUMBER error when attempting to activate your product on Office.com/setup and you see one of the following error messages, you should start by checking the status of the Microsoft Office servers:

  • “Sorry, we can’t set up your account right now. Hang on to your product key, and try again later. If this happens again, contact support.”
  • “Sorry, we can’t find this product key in our database.”
  • “Sorry, we can’t set up your account right now”

Each of these 3 messages will appear in situations where you enter a product key that is actually for an older version of Office – One that isn’t available for download on Office.com /setup.

In case this scenario is applicable to your particular scenario, you will need to use different links (depending on your Office version) to activate your Office suite.

In the event that you’ve already used the correct link and you’ve ensured that your license key is valid, move down to the next method below.

Method 3: Dealing with a Volume license key

If you followed the instructions above and you’re still experiencing the same problem, it’s possible that you’re actually dealing with a volume license key. These things are typically used by organizations to activate volume editions of Office Professional Plus.

If this scenario is applicable, you can activate your volume edition either via MAK (Multiple Activation Key) or via Key Management Service (KMS).

Note: If you have a system administrator, contact it for assistance on activating via KMS.

If you don’t have a system administrator, follow the instructions below to activate via MAK:

  1. Open your Office installation (2013, 2016 or 2019) and go to File > Account and click on Change Product Key.
    Changing the Product key
  2. When asked to do so enter the MAK key and submit it, then follow the on-screen prompts to complete the key entry process.
    Note: After you enter a valid product key, you will be given two verification methods – Internet and Telephone activation. Choose whichever method you feel more comfortable with, but keep in mind that Internet Activation is way faster since you will not have to wait to get in touch with a customer service representative.
  3. Once the activation procedure is successful, close your Office program and restart your computer.
  4. After the next startup is complete, open an Office program once again and go to File > Account (or File > Help in Office 2010 or older) and see if your Office installation displays as a Licensed Product or Product Activated on newer versions.
    Example of an Activated Product

In case you’re not using a volume license key or you have previously used a one-time purchase license, move down to the next potential fix below.

Method 4: Re-activating a One-Time Purchase license

If you have previously used an Office one-time purchase license that only allows you to install it on one computer at a time and you didn’t uninstall the suite before resetting your computer or selling your computer, Microsoft activation server might trigger the ERR_MISSING_PARTNUMBER error because it thinks you are actually trying to install the Office suite more than once.

In the event that this scenario is applicable, you should get in contact with a Microsoft live agent and ask them to activate your license key.

To do this, simply open a ticket using this link (here), describe your issue as best you, and click on the Get help button. Next, scroll down through the list of self-help solutions and click on the Sign In button (under Get more Help)

Getting in touch with a Microsoft Live Agent

Next, once you have successfully signed in with your Microsoft account, choose to get in contact with a live agent, then follow the on-screen instructions to get in touch with one.

Keep in mind that once you get in touch with a Microsoft agent, you will be asked a couple of security settings in order to confirm that you are actually the owner of the license key that you are trying to activate. If everything checks out, they will activate your Office license remotely.


Kevin Arrows

Kevin Arrows is a highly experienced and knowledgeable technology specialist with over a decade of industry experience. He holds a Microsoft Certified Technology Specialist (MCTS) certification and has a deep passion for staying up-to-date on the latest tech developments. Kevin has written extensively on a wide range of tech-related topics, showcasing his expertise and knowledge in areas such as software development, cybersecurity, and cloud computing. His contributions to the tech field have been widely recognized and respected by his peers, and he is highly regarded for his ability to explain complex technical concepts in a clear and concise manner.