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Windows Server MAK Key Shows Already Used (0xC004C020) After HDD-to-SSD Migration and Old HDD Formatted

Lim Kai Zhi 0 Reputation points
2026-06-05T00:07:55.7+00:00

Hi,

I am using a Windows Server MAK product key. The server was previously activated successfully.

Recently, I replaced the HDD with an SSD and migrated the system. The old HDD has since been formatted. After the migration, Windows now requires activation. When I enter the same MAK product key, activation fails with error 0xC004C020 and indicates that the product key has already been used.

Is there any way to reactivate Windows using the existing MAK key? Does the MAK activation count need to be reset by Microsoft, or is there another solution available?

Thank you.

Windows for business | Windows Server | Devices and deployment | Licensing and activation
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  1. Jason Nguyen Tran 18,980 Reputation points Independent Advisor
    2026-06-05T01:03:44.5433333+00:00

    Hi Lim Kai Zhi,

    The error 0xC004C020 is common with Multiple Activation Keys (MAK). Each MAK has a limited number of activations tied to Microsoft’s activation servers. When you migrated from HDD to SSD, Windows treated the hardware change as a new activation request, which consumed another count. Since the old HDD was formatted, the activation record cannot be reused.

    The good news is that you don’t need to wipe the system. You have two main options:

    (1) If your MAK still has unused activations, you can run slmgr /ato to attempt activation again, or use the phone activation method (slui 4) to complete it manually.

    (2) If the activation count has been exhausted, you’ll need to contact Microsoft Volume Licensing Support to request a re‑issue or reset of the activation count. They can validate your license and allow additional activations for legitimate migrations like yours.

    In the meantime, make sure your system is fully updated and that the key is entered correctly with slmgr /ipk <your key>. If you are part of a licensing agreement, your IT admin or reseller can also help escalate the request to Microsoft.

    I hope the response provided some helpful insight. If you find this answer useful, please hit “accept answer” so I know it addressed your concern.

    Jason.

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  2. AI answer

    2026-06-05T00:08:10.5533333+00:00

    Error 0xC004C020 means the Multiple Activation Key (MAK) has exceeded its activation limit. By design, a MAK can only be used a limited number of times. After replacing the HDD with an SSD and reactivating, the key has now hit that limit.

    To continue using the same MAK key, the activation count must be increased by Microsoft. The supported path is:

    1. Verify that the MAK being used is the one originally provided for this server.
    2. Contact the Microsoft Licensing Activation Centers and request additional activations (an increase of the MAK activation limit or an extension). Provide the MAK and proof of entitlement when requested.
    3. After Microsoft increases the activation allowance, run activation again on the server using the same MAK.

    If online activation still fails after the limit is raised, use telephone activation with the same MAK as instructed by the Activation Center.

    There is no supported way to “reset” the count locally; it must be adjusted by Microsoft.

    References:

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