Quick answer
First check whether Windows is activated at all and what error it reports, then whether the computer has internet and the correct date and time. Next, determine whether the license is digital (linked to a Microsoft account or motherboard) or a 25-character key. If the error persists after that, note its code and contact support.
How to recognize the problem
- Settings shows a message that Windows is not activated
- Watermark in the bottom right corner of the screen
- Activation reports an error with a code (e.g. 0xC004F074)
- Some personalization options are locked
- Activation asks for a key even though Windows was previously activated
Most common causes
No internet connection
Standard activation must contact Microsoft servers. Without a connection or behind a restrictive firewall, activation cannot complete.
Incorrect date and time
If the computer clock is off, the secure connection certificate is rejected and activation reports an error.
Motherboard changed or reinstallation
A digital license is tied to hardware. After major part replacements, Windows asks for reactivation.
Key entered incorrectly or for a different version
One wrong character or a Windows 10 Home key on Windows 11 Pro leads to rejection.
License linked to another Microsoft account
If you are signed in with a different account than at purchase, the system does not see the digital license.
Step-by-step fix
- 1
Check current activation status
Open
Settings > System > Activation(Windows 11) orSettings > Update & Security > Activation(Windows 10) and see what it says under status. If it says Windows is activated, the problem is probably in the display or a single app, not the license. If it says not activated, click the item with details and note the exact text and error code if present. - 2
Check internet connection
Open a browser and load any page. If pages do not work, fix the connection first, because standard activation cannot succeed without internet. At work, check whether you are on a network that allows access to Microsoft servers, not just the internal network.
- 3
Set the correct date and time
Go to
Settings > Time & Language > Date & timeand turn on automatic time and time zone setting. Click the sync button if available. Then try activation again. - 4
Determine license type
In the same
Activationwindow, check whether it says the license is digital and linked to a Microsoft account. If so, sign in with the account you used at purchase or first activation. If you have a 25-character key, prepare it and watch for easily confused characters. - 5
Run the troubleshooter
In the
Activationwindow, open the activation troubleshooter. Windows will try to find the license itself and suggest the next step. If it asks for a Microsoft account, sign in with the same account under which the license is registered. - 6
Enter the key carefully
If you have a key, choose the option to change the product key and enter it without spaces. Check that the key matches the version and edition (Home or Pro). If the system reports that the key is already used, do not enter it multiple times; move on to checking the account.
- 7
Check that the account is correct
Sign out and sign back in with the Microsoft account linked to the license. If you use a work account at a company, check whether the administrator assigns the license via the Microsoft 365 portal. A license assigned to an account appears only after signing in with that account.
- 8
Note the error code and search for it
The error code is the most useful piece of information. Note it and look for the official explanation on Microsoft support pages. Do not download "activators" or unknown tools, as they often carry malware and violate the license terms.
If nothing helps
If you have checked the connection, time, account and key, and activation still fails, the problem is probably on the license side, not the computer. In that case, contact the seller from whom you bought the license or Microsoft support and provide the exact error code, the Windows version (Settings > System > About) and whether the license is digital or a key. If the computer is from a company, contact the administrator who manages the Microsoft 365 license, as they can check the assignment without reinstalling. Do not try to "clean" the system by deleting activation files or editing the registry, as this rarely solves the problem and can lock the license and make later activation harder.
How to prevent it
- Link the digital license to your Microsoft account immediately after first activation
- Keep the key and proof of purchase in a safe place
- Keep automatic time setting turned on
- Before reinstalling, check whether Windows is activated and note the license type
When to call a professional
If the computer is at a company or the license comes through a Microsoft 365 subscription, it is better to contact the administrator or IT support than to change keys and accounts yourself. A professional can check the license assignment and prevent the same license from accidentally being linked to the wrong account.
IT infrastructure maintenance · Servers, networks, backup, security and helpdeskFAQ
Is internet required to activate Windows?
Yes, standard activation requires a connection to Microsoft servers. Without internet, the system may show a message that activation is not possible, even when the license is valid.
Windows was activated, now it is not. What changed?
Most often hardware was changed, such as the motherboard, or a reinstallation was performed. The digital license must then be re-linked to the Microsoft account or activated with a key.
Can I use Windows that is not activated?
You can start it, but some personalization options are locked and a notice that Windows is not activated appears on screen. For business computers, the license must be valid due to the terms of use.