I use to generate the ogp tags in themes I code but this commercial one is beyond my knowledge. The client want to share a page but any image option shows up.
Instead of a
taxonomy-name.php template file, this theme rely on a page templates, where user choose the category/taxonomy to display the gallery from. Problem is: I can't get the attachments as the gallery renders after the query, I do will ask the theme autor to implement this but right now I need to fix this some way.