Error 0xC004C003 — Product key is blocked

Error 0xC004C003: Product Key is Blocked

This error occurs in: Windows 10, Windows 11, Windows 8.1, Windows 7.

Cause

The product key has been blocked by Microsoft — usually because it was previously used too many times, came from an illegal source, or is an OEM key used outside the permitted scope.

Symptoms

• During activation, the message appears: "Product Key is Blocked"
• Error code: 0xC004C003
• English version: "The activation server determined the specified product key is blocked"

Step-by-Step Solution

Contact the key seller for a replacement. If the key was purchased legally, contact Microsoft support with proof of purchase.

Method 1: Reactivation through Settings

1. Open Settings → System → Activation
2. Click Troubleshoot (if available)
3. Click Change product key
4. Enter the key from KluczeSoft and click Next → Activate

Method 2: Activation via Command Line

Open Command Prompt as Administrator and enter:

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

Replace XXXXX-... with your product key.

Method 3: Phone Activation

If online activation does not work:

slui 4

Call the displayed number and follow the instructions.

Verification

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

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

Still Not Working?

If the above steps did not help:

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