Below are the most frequent activation issues users face—and how to fix them like a pro.

1. Error Code 0xC004C003

Problem: The activation server determined the key is blocked.

Solution:

• Double-check if you installed a genuine Windows 11 key.
• If upgrading from Windows 10, ensure your device had a properly activated version of Windows 10.
• Reconnect to the internet and retry activation.
• If persistent, consider purchasing an authentic key from Codesforever.

2. Error Code 0x8007007B

Problem: Windows cannot find the activation server.

Solution:

• Connect to a different network (e.g., switch from Wi-Fi to Ethernet).
• Ensure DNS settings are correctly configured.

Use Command Prompt to manually enter the activation key: 

slmgr.vbs /ipk YOUR-PRODUCT-KEY

slmgr.vbs /ato

3. Activation Error After Hardware Changes

Problem: Changing your motherboard or hard drive can deactivate Windows.

Solution:

• Log in using the Microsoft Account tied to your digital license.
• Navigate to Settings → Activation → Troubleshoot.
• Select I recently changed hardware and follow the prompts.

According to Microsoft's official Activation Troubleshooter guide, this method resolves over 80% of post-hardware change issues.

4. Invalid Product Key Error

Problem: Entered key is invalid or incorrect.

Solution:

• Verify you're using a Windows 11 Pro key if you're installing Windows 11 Pro.
• Purchase a Microsoft-verified key from a trusted reseller like
  CodesForever.
• Never trust free product keys—these often cause issues later and violate Microsoft’s licensing terms.