Entering current 3 computer licence key to my wife`s laptop

I have a current License for 3 computers running till September 2018 but cannot enter it into my wife`s laptop,  keep getting invalid.
She is running Free version .

Hi Alan,
We understand your concern and to assist with the issue better please kindly provide order reference number for the subscription for 3 computers. please feel free to contact us. We are always here to help you with your issue. we work round the clock.
Thank you.