Error 0xC004C021 — MAK key extension limit exceeded

Error 0xC004C021: Multiple Activation Key (MAK) extension limit exceeded

This error occurs in: Windows 10, Windows 11, Windows Server.

Cause

The MAK key activation limit cannot be extended further. The key has reached the maximum allowed extension limit.

Symptoms

• During activation, the message appears: "Multiple Activation Key extension limit exceeded"
• Error code: 0xC004C021
• English version: "The Multiple Activation Key extension limit has been exceeded"

Step-by-step solution

Contact Microsoft Licensing or your volume license provider to obtain a new MAK key or a KMS key.

Solution for Windows Server

1. Open PowerShell as administrator
2. Enter the key:

slmgr /ipk XXXXX-XXXXX-XXXXX-XXXXX-XXXXX

1. Activate:

slmgr /ato

1. Check the status:

slmgr /xpr

Verification

After performing the steps, check if the activation was successful:

• Windows: Settings → System → Activation → should be "Windows is activated"
• Or: slmgr /xpr in the command line

Still not working?

If the above steps did not help:

1. Check the date and time — they must be correct (an incorrect date can block activation)
2. Temporarily disable antivirus and try again
3. Check the internet connection — online activation requires a connection to Microsoft servers
4. Contact us:
   • Email: [email protected]
   • Phone: 00 800 121 1654 (toll-free)
   • Help center: pomoc.kluczesoft.pl