Hi there,
Thanks for reaching out!
The message doesn’t specifically refer to your story’s poster image. What might be triggering the warning on that particular story is the image on the very last page, which is smaller than the other ones (1024px wide vs 1200px wide). You could try using a larger original image there. After that, wait for Search Console to check your content again.
Generally for Search Console questions I recommend reading their documentation and asking in the Search Central community forums for assistance, as that’s the best place to get answers for all things Search Console. Here we focus on WordPress-specific issues.
Hope that helps!
Thanks! I made the image be 1200 x 800 and while I’m not sure it solved the problem as when I inspect it, the warning still appears: https://ibb.co/dDF1R7f.
However, if I live test it, it goes away: https://ibb.co/NT8PmwP.
Either way you can close this out on your end as if it comes back as failed, the next step is the Google support forums.