Sorunu çözdüm, belki işine yarayan olur;

have_posts ve while açıldığı için ve aşağıda kapatıldığı için araya } sokulmaması gerekiyor. while ve ifi kapatmadan araya } sokmamak gerekiyor.

<ul id="listPage" class="row item-list">
                                <?php if (is_page(array('?sortby=asc', '?sortby=desc'))) { ?>
                                  <?php if ( $newQuery->have_posts() ) : while ( $newQuery->have_posts() ) : $newQuery->the_post(); ?>
                                    <li class="col-12 col-sm-12 col-md-12 col-lg-4 col-xl-4 column items-col">
                                        <div class="item">
                                            <a href="<?php the_permalink(); ?>" style="color: <?php echo $rl_category_color; ?>;" class="d-flex align-items-center">
                                                <div class="in">
                                                    <div class="d-flex justify-content-between author">
                                                        <div class="author-name col-7">
                                                            <br><br>
                                                            <?php
                                                                $author = get_post_meta( get_the_ID(), 'postAuthor', true );
                                                                if(!empty($author)) {                                                      
                                                                    foreach ($author as $author_item => $item) {
                                                                        echo get_the_title($item).'<br>';
                                                                    }
                                                                }
                                                            ?>
                                                        </div>
                                                        <div class="rank col-5 text-end">
                                                            <br><br>
                                                            <?php
                                                                $konu = get_the_category( get_the_ID() );
                                                                foreach ($konu as $item) {
                                                                    $konu_name = $item->name;
                                                                }
                                                                echo $konu_name;
                                                            ?>
                                                        </div>
                                                    </div>
                                                    <figure>
                                    <img src="<?php the_post_thumbnail_url('full'); ?>" alt="<?php the_post_thumbnail_caption();?>" class="img-fit">
                                </figure><br>
                                                    <div class="title"><?php echo title_limit(40); ?></div>
                                                    <p><?php echo icerik_limit(get_the_content(), 150); ?></p>
                                                </div>
                                            </a>
                                        </div>
                                    </li>
                                    <?php endwhile; endif; } else if (have_posts()) : while (have_posts()) : the_post(); ?>
                                    <li class="col-12 col-sm-12 col-md-12 col-lg-4 col-xl-4 column items-col">
                                        <div class="item">
                                            <a href="<?php the_permalink(); ?>" style="color: <?php echo $rl_category_color; ?>;" class="d-flex align-items-center">
                                                <div class="in">
                                                    <div class="d-flex justify-content-between author">
                                                        <div class="author-name col-7">
                                                            <br><br>
                                                            <?php
                                                                $author = get_post_meta( get_the_ID(), 'postAuthor', true );
                                                                if(!empty($author)) {                                                      
                                                                    foreach ($author as $author_item => $item) {
                                                                        echo get_the_title($item).'<br>';
                                                                    }
                                                                }
                                                            ?>
                                                        </div>
                                                        <div class="rank col-5 text-end">
                                                            <br><br>
                                                            <?php
                                                                $konu = get_the_category( get_the_ID() );
                                                                foreach ($konu as $item) {
                                                                    $konu_name = $item->name;
                                                                }
                                                                echo $konu_name;
                                                            ?>
                                                        </div>
                                                    </div>
                                                    <figure>
                                    <img src="<?php the_post_thumbnail_url('full'); ?>" alt="<?php the_post_thumbnail_caption();?>" class="img-fit">
                                </figure><br>
                                                    <div class="title"><?php echo title_limit(40); ?></div>
                                                    <p><?php echo icerik_limit(get_the_content(), 150); ?></p>
                                                </div>
                                            </a>
                                        </div>
                                    </li>
                                    <?php endwhile; endif; ?>