WordPress Custom Post Type not showing in Search Results

I have an issue with custom post types(Quiz) & search in WordPress. Custom post types are not showing in my search result page. Only the default post content is showing in my search result.

Following are the codes I used

functions.php function create_posttype() {

register_post_type( 'compassquiz',
    array(
        'labels' => array(
            'name' => __( 'Compass Quiz' ),
            'singular_name' => __( 'Compass Quiz' )
        ),
        'taxonomies' => array('post_tag'),
        'public' => true,
        'publicly_queryable' => true,
        'has_archive' => true,
        'rewrite' => array('slug' => 'free-quiz-bank-exam'),
        'query_var' => true,
        'exclude_from_search' => false,
    )
);}

add_action( 'init', 'create_posttype' );

Additional code in functions.php

//Read Custom Post types in Search
function filter_search($query) {
    if ($query->is_search) {
    $query->set('post_type', array('post', 'compassquiz'));
    };
    return $query;
};
add_filter('pre_get_posts', 'filter_search');

search.php

<?php
    if ( have_posts() ) : ?>
        <header class="page-header">
            <h1 class="page-title">
                <?php printf( esc_html__( 'Search Results for: %s', 'compass' ), '<span>' . get_search_query() . '</span>' ); ?>
            </h1>
        </header>
<?php

    while ( have_posts() ) : the_post();
        get_template_part( 'template-parts/content', 'search' );
    endwhile;
        the_posts_navigation();
    else :
        get_template_part( 'template-parts/content', 'none' );
    endif; 
?>

content-search.php

<article id="post-<?php the_ID(); ?>" <?php post_class(); ?>>
    <header class="entry-header">
        <?php the_title( sprintf( '<h2 class="entry-title"><a href="%s" rel="bookmark">', esc_url( get_permalink() ) ), '</a></h2>' ); ?>
    </header>

    <div class="entry-summary">
        <?php 
            echo substr(get_the_excerpt(), 0,150) . '...'; 
            echo ('<br><a href="' .get_permalink() . '" class="moretag">Read More &raquo;</a>');
        ?>
    </div><!-- .entry-summary -->
</article><!-- #post-## -->

I have tried lots of code found in WP Fourm & also in other stackoverflow questions. But couldn’t find a solution that actually work.

Answer

Add this code in search form. set custom post type in hidden field value.

<input type="hidden" name="post_type" value="post type name" />

---

multiple custom post type in search form

<input type="hidden" name="post_type" value="posttype1, posttype2, posttype3" />