Some licenses are tied to specific hardware and can only be activated once. If you try to use the key more than once, this can cause problems. In such cases, you can try manually entering the key via the command line or contact Microsoft support for activation over the phone. It is also worth checking that your key matches the version of Windows you have installed. If you are considering using third-party activation programs such as , I would recommend being careful and understanding all the risks associated with using illegal methods.