Create Custom Event for post with specific meta_key value

Hi there,

I would like to assign points to users who post a custom post type (‘job_listing’) where the meta_key ‘_case27_listing_type’ has the value ‘probiotics’.
I wrote the code below based on your documentation but it’s not working. If I remove $listing_type == ‘probiotics’ from the if statement on the listener then it works, ie. assigns points, but targets all custom post types with any value of ‘_case27_listing_type’. Where am I going wrong?

add_filter( 'gamipress_activity_triggers', 'activity_trigger_listings' );

function activity_trigger_listings( $triggers ) {

    // Replace this with the CPT you want, for example: event
    $listing = 'job_listing';

    $post_type = get_post_type_object( $listing );

    $triggers[__( 'Listings', 'gamipress' )] = array(
        'gamipress_publish_listing' => sprintf( __( 'Publish a %s', 'gamipress' ), $post_type->labels->singular_name ),
        'gamipress_delete_listing' => sprintf( __( 'Delete a %s', 'gamipress' ), $post_type->labels->singular_name ),
    );

    return $triggers;

}

add_action( 'transition_post_status', 'listener_trigger_listings', 10, 4 );

function listener_trigger_listings( $new_status, $old_status, $post, $listing_type ) {

    global $post;

    $post_id = $post->ID;
 	$listing_type = get_post_meta( $post_id, '_case27_listing_type', true );

    // Check if post status transition come to publish
    if ( ( $new_status == 'publish' ) && ( $old_status != 'publish' ) && ( $listing_type == 'probiotics' ) ) {

        // Trigger content publishing actions
        gamipress_trigger_event( array(
            'event'      => 'gamipress_publish_listing',
            'user_id'    => get_current_user_id(),
        ) );
    
    }
}

Any help you can provide would be greatly appreciated.

Isabel