It is necessary for you to contact Adobe Support. You can start a chat session by clicking on the blue Contact Us button under the Help and Support menu at Adobe.com. Or you can contact Support by telephone using the numbers listed here: https://helpx.adobe.com/contact/phone.html. Support is only available during business hours in Europe.
Tell them that you only want them to deactivate your serial number. If they try to tell you that Elements 14 is not supported, ask to speak with a supervisor. They are required to deactivate the machine to which you no longer have access.