An activation problem is not something we can help you with. Try contacting Elements support. You can start a chat session by clicking on the blue Contact Us button under the Support menu at Adobe.com. Or you can contact Support by telephone using the numbers listed here: https://helpx.adobe.com/contact/phone.html. Unfortunately, it is my understanding that support is only available in Europe during normal work hours. If they tell you that they do not offer support for Elements 2018 tell them clearly that you only want to deactivate your license.