Keep in mind that it's always best to use an official Windows product key for activation. Activation of Windows through Command Prompt and KMS servers is usually only intended for mass volume ...

Fix Error 0xC004C003, 0xC004C003, The activation server determined the specified product key is blocked, on Windows 11/10, by following this guide.

This action refreshes the operating that removes corrupt data that could be causing Windows activation errors to appear. Solution 1: Run Windows Activation Troubleshooter ...

Guide to fix Windows 11/10 Activation or Update Error 0x800f0805. Depending on which situation you are in, follow those solutions here.

Microsoft has shared a workaround for customers experiencing 0xc004c003 activation failures on Windows 10, version 2004 and 20H2 devices after installing the January 2021 monthly "C" release ...