I attempted several suggestions under this thread and from my external searches but it was a whole other problem for me. My specific instruction to use an image indicated by the og:image tag was being overridden by the open graph tags supplied by the Jetpack plugin. you can find my detailed answer here. However, I thought it worth to add the steps in brief on this more-followed thread. Hope this helps someone.
The Facebook Sharing Debugger helped me identify the root cause and from there, I followed these steps:
- Debug your website using the debugger above. Simply type in the URL and hit debug. This should give you a list of warnings and once you scroll down to the open graph tags sections, you will be able to see the values that are being fetched for your website. The one to focus on is the og:image tag.
- Scroll further down to the "See exactly what our scraper sees for your URL" link and search for the og:image tag to find the villain in your story.
- Now simply, opt the means to remove an override that is occurring. In my case, I found the following function helpful. It changes the default image used any time Jetpack can not determine an image to use.
It changes the default image used any time Jetpack can not determine an image to use
function custom_jetpack_default_image() {
return 'YOUR_IMAGE_URL';
}
add_filter( 'jetpack_open_graph_image_default', 'custom_jetpack_default_image' );
I should add that the image parameters such as minimum 300px x 200px and size < 300 KB are recommended. And please follow these instructions if such general instructions do not work for you, because, then it is most likely that your issue is similar to mine. Also, sometimes the simplest solution may just be to remove the plugin (provided you verify that you can do without it).
At the end you should be able to see something like - 
Hope this helps.
NS