i have the same exact problem since forever now, and it was not even fixed with “Thumbnail Fixer for Facebook” plugin at all.

before the plugin i had these errors:

“The ‘og:image’ property should be explicitly provided, even if a value can be inferred from other tags.”
“The following required properties are missing: og:url, og:type, og:title, og:image, og:description, fb:app_id”

and after the plugin:
“The provided ‘og:image’ properties are not yet available because new images are processed asynchronously. To ensure shares of new URLs include an image, specify the dimensions using ‘og:image:width’ and ‘og:image:height’ tags.
Learn More: https://developers.facebook.com/docs/sharing/best-practices/#precaching”
“The following required properties are missing: fb:app_id”

so how could i get it working.