If you are receiving error code 0xC004E028 when trying to activate your Windows it means that your computer is already in the process of activation. During the activation process, Windows sends out the Key to Microsoft servers to validate it.

Sometimes validation takes a long time, and if you try to activate it again, you will receive this error code 0xC004E028. I will suggest you wait and only activate if the activation fails. Else you should be good to go.