Images not showing when sharing

I see numerous posts about this problem — no images showing up on FB and Twitter shares, but no solutions. Has anyone fixed this issue? If so, how? I had Youst but that didn’t work, so I switched to this plugin and it doesn’t work for that either. (Yes, I disabled the other one.)
Of interest, this wasn’t a problem until a few months ago. Who has this problem? Who has fixed it?
Thanks!