Hi ElaineG, Click on the Parallels Desktop menu, and select Account & License. In the activation window, click on your account email address and select Sign Out. If you try to use the license on a new Mac without signing out of the old one, then upon activation on the new Mac you will see a warning that the license is already in use. If you click on Activate on This Mac, the current copy will be successfully activated, and the license will automatically be deactivated on the old Mac. If the issue persists, please provide your activation key in the private message, we are here to help!