Often your WordPress website will have custom post types such as books, videos, galleries, events, portfolio. My question is: Did you know that these will not automatically be included in your site’s main RSS feed? If you start developing your site a little more and end up creating a custom post type, you’ll soon realise that your readers aren’t getting that information unless you intervene.

Your main WordPress RSS feed only includes “Posts” not even pages, so custom post types are a long shot.  This WordPress article shows how you can add custom post type content to your WordPress RSS Feed. It’s a quick fix and it just requires a little snippet with very little customisation.

You would need to open your theme’s functions.php file and add the following code within the PHP markup:

function sofw_request($qv) {
    if (isset($qv['feed']) && !isset($qv['post_type']))
        $qv['post_type'] = array('post', 'video', 'gallery');
    return $qv;
}
add_filter('request', 'sofw_request');

You can add as many or as few as you want but you should know that you must leave post in there if you want to keep your posts in the RSS feed.