add_action( 'learndash_quiz_completed', 'quiz_completed', 5, 2 );

    function quiz_completed( $data, $user ) {

        if( isset( $data['quiz']->ID ) ) {
            $quiz_id = $data['quiz']->ID;
        } else {
            // For grading in the admin
            $quiz_id = $data['quiz'];
        }

        $settings = get_post_meta( $quiz_id, 'wpf-settings', true );

        if ( $data['pass'] == true && ! empty( $settings['apply_tags_ld'] ) ) {

            wp_fusion()->user->apply_tags( $settings['apply_tags_ld'], $user->ID );

        } elseif ( $data['pass'] == false && ! empty( $settings['apply_tags_ld_quiz_fail'] ) ) {

            wp_fusion()->user->apply_tags( $settings['apply_tags_ld_quiz_fail'], $user->ID );

        }

    }