Blank Images on Facebook After Postings via Publicize

Hi There:
I’ve been putting up with this problem for over a year, and I want to try and close this loop, but I’m having trouble doing so.

I have seen more than one post during my recent research about the issues with posts on Facebook from WP posts coming up with blank images. Usually, I have an image within the body of the blog post at the top-left. I have tried Featured Image for this last try, but I might have to have a different size because I’m not cool with the way it gels within the Twenty Sixteen theme, which I’ve updated to just over a week ago.

I have tested my recent post via its URL in the Facebook debugger, and it gives me warning, but not really any guidance on how best to resolve this issue. The other ways I tried have not fixed the issue for me, so I’m a bit lost and frustrated.

I could use some guidance on resolving this, as obviously the blank images look very unsightly.

Thanks much!