Error Page not found

We have changed the theme of our website. When we post photos to our facebook page we get an error” Page not found”
here is the page: https://www.arch2o.com/tobin-center-for-the-performing-arts-lmn-marmon-mok/
and here is the facebook link: https://www.facebook.com/Arch2O.Magazine/posts/1879617042049647
here is what we did so far to discover the issue:
1- changing the theme, gave the same error
2- turning off SEO Yoast, No Error
3- Chrome page inspect, no errors
What should we do next?

debugging the facebook page gives the following error
? Inferred Property
The ‘og:image’ property should be explicitly provided, even if a value can be inferred from other tags.
? Missing Properties
The following required properties are missing: og:url, og:image, og:description
? Bad Response Code
URL returned a bad HTTP response code.

The page I need help with: [log in to see the link]