A link to your site/post where this happens would help further troubleshooting.
My guess is that somehow the author avatar gets higher priority in code than your feature image. And if your theme doesn’t specify the feature image through opengraph tags to be the “go to image for sharing”, the social platforms then take the first image they can grab from your post/page.
If your theme doesn’t use proper opengraph tags, you can always use a wordpress plugin that adds/specify those tags for you https://wordpress.org/plugins/search/opengraph+plugins/
Thanks for taking a look at it.
I set the featured image before published it and I cleared the cache. It seems like it will show the featured image if I share it on FB. However, I tried to share it on Google Chat and it showed the author box. Do you know how can I fix that?
Thank you so much.
The only way you can force the featured image to show on any/all social media platforms is to have the opengraph tags added right.
Please take a look at plugins that can do that for you https://wordpress.org/plugins/search/opengraph+plugins/