Sometimes, when trying to share something on social media, a wrong image shows or no image at all. Then go through the following steps:
Check whether you have set the meta-data. Here you can read how to adjust the title, description and image (meta data) of a page.
Clear your cache (your browser's memory). In this article you can read how to do that. Please note: it can sometimes take a while before you see the correct image when sharing. Try again the next day.
Make the social media platform aware of the existence of your image. You can "ask" the provider to find the image by copying the URL of the page you want to share and pasting it into the relevant tool:
Good luck!