Twitter card not working for blog posts

I have another website using another theme and I don’t have this issue (and I haven’t installed any social SEO or sharing plugin). This is not happening when tweeting youtube’s url, the thumb is automatically generated. I tried the twitter validator https://cards-dev.twitter.com/validator and I got the following error:

INFO:  Page fetched successfully
INFO:  5 metatags were found
ERROR: No card found (Card error)

It seems that the page (website) needs to include metadata to show the image: https://twittercommunity.com/t/error-no-card-found-card-error/107179

Any help is appreciated.

Thanks,
Claudia

• This reply was modified 5 years ago by claubs.

I was able to fix it just adding the following code to the child theme. Just sharing the code just in case helps someone else:

add_action('wp_head', 'add_twitter_cards');
function add_twitter_cards() {
    if(is_single() || is_page()) {
        $tc_url    = get_permalink();
    	$tc_title  = get_the_title();
    	$tc_description   = get_the_excerpt();
    	$tc_images = wp_get_attachment_image_src( get_post_thumbnail_id($post->ID), full );
    	$tc_image_thumb  = $tc_images[0];
		if(!$tc_image_thumb) {
   		   $tc_image_thumb = 'my-url-for-page-thumbs';
  		}
    	$tc_author   = str_replace('@', '', get_the_author_meta('twitter'));
?>
    <meta name="twitter:card" value="summary" />
    <meta name="twitter:site" value="@my-twitter-account" />
    <meta name="twitter:title" value="<?php echo $tc_title; ?>" />
    <meta name="twitter:description" value="<?php echo $tc_description; ?>" />
    <meta name="twitter:url" value="<?php echo $tc_url; ?>" />
    <meta name="twitter:image" value="<?php echo $tc_image_thumb; ?>" />
    <?php if($tc_author) { ?>
        <meta name="twitter:creator" value="@<?php echo $tc_author; ?>" />
	<? }
    }
}
?>

All the best,
Claudia