@itagility
I had the same problem. Solved by adding this function to my theme’s functions.php:
add_filter(‘instant_articles_transformed_element’, ‘my_subtitle’, 10, 1);
//the filter is provided by the fb-instant-articles plugin
//it passes in the instant_article object, which you can modify
//before it finishes rendering the feed.
function my_subtitle($article) {
global $post;
$my_subtitle = get_the_excerpt(); //replace this with whatever
//the instant article has a Header element, which has a subtitle property.
//Get it and add a subtitle
$subtitle = $article->getHeader()->withSubTitle($my_subtitle);
//return the modified instant article back into the render flow
return $article;
//verify that your /feed/instant-articles contains <h2>’s in each feed item <content> elements.
}
