please tell me whats wrong? I have post type + custom taxonomy, i need display via shortcode with my posts in post type via category params:

function list_faqs_shortcode( $atts ) {

    // Parse your shortcode settings with it's defaults
    $atts = shortcode_atts( array(
        'category' => ''
    ), $atts, 'myprefix_custom_grid' );

    // Extract shortcode atributes
    extract( $atts );
    
    $categories  = explode(',', $atts['category']);
    
    // Define output var
    $output="";

    // Define query
    $query_args = array(
        'post_type'      => 'cstore_faq', // Change this to the type of post you want to show
        'posts_per_page' => $posts_per_page,
    );

    // Query by term if defined
    if ( $term ) {

        $query_args['tax_query'] = array(
            array(
                'taxonomy' => 'category_list',
                'field'    => 'term_id',
                'terms'    =>  $categories,
                //'terms'    => $term,
            ),
        );

    }
    echo $categories;

    // Query posts
    $custom_query = new WP_Query( $query_args );

    // Add content if we found posts via our query
    if ( $custom_query->have_posts() ) {

        // Open div wrapper around loop
        $output .= '<div>';

        // Loop through posts
        while ( $custom_query->have_posts() ) {

            // Sets up post data so you can use functions like get_the_title(), get_permalink(), etc
            $custom_query->the_post();

            // This is the output for your entry so what you want to do for each post.
            $output .= '<div>!!' . get_the_title() . '!!</div>';

        }

        // Close div wrapper around loop
        $output .= '</div>';

        // Restore data
        wp_reset_postdata();

    }

    // Return your shortcode output
    return $output;

}
add_shortcode( 'faq_list', 'list_faqs_shortcode' );

and my shortcode:
[faq_list category=”77″]

but not displayed nothing, if i try display like [faq_list] my posts all displayed correctly, whats wrong? thank you.