Just for clarification, are you talking about the open graph preview image not showing up when sharing via WhatsApp?
What do you see now? Nothing? Something you didn't expect to see?
Debugging OpenGraph issues with Facebook is very hard. Many times we have found that facebook caches the OpenGraph metadata and although you change it (either adding new values or changing old ones), Facebook refuses to refresh it.
Our suggestion is to check always with newly created URLs to avoid Facebook caches.