If you have updated your existing system to Windows 10, the
error 0xC004F034 license could not be found or was invalid can occur. In this case, whether your personal license key or the Microsoft-Server are to blame, we clarify in this article.
Fix Activation Problems After Upgrade:
If Windows 10 can not be activated after an upgrade, the error is not due to your key, but Microsoft's servers. These servers are very busy after the big rush to the new operating system.
To activate your copy of Windows, click the bottom left of the Windows icon and choose the "Settings".
In the category "Update and Security", click on the tab "Activation".
Here you click on the button "Activate" and wait until the process is complete.
If an error message appears, just try it again. In the test, it worked for the fifth time. Alternatively, you can wait a few days and start the activation again.