Custom Entry Meta Error

I came up with the following code (based on your documentation and answers to previous support threads) to display the entry meta within a div (above the entry content and sidebars). It displays most of it, but not the author name or local avatar. Any idea why? I’d appreciate your help with this.

<?php if (is_single()) : ?>
                        <div class="entry-meta">
                            <?php
                            $author_id = get_the_author_meta('ID');
                            $user_nicename = get_the_author_meta('user_nicename');
                            $avatar_filename = sanitize_file_name($user_nicename) . '.webp';
                            $upload_dir = wp_upload_dir(null, false);
                            $avatar_path = $upload_dir['basedir'] . '/avatars/' . $avatar_filename;
                            $avatar_url = $upload_dir['baseurl'] . '/avatars/' . $avatar_filename;

                            // Check if the local avatar file exists, otherwise use default avatar
                            $avatar_html = file_exists($avatar_path)
                                ? sprintf('<img src="%s" alt="Author Avatar" width="96" height="96">', esc_url($avatar_url))
                                : get_avatar($author_id, 48);

                            printf(
                                '<div class="author-wrap">
                                    <span class="author-label">Written by</span>
                                    <a href="%1$s" title="%2$s" rel="author">
                                        <span class="author-name" itemprop="name">%3$s</span>
                                    </a>
                                </div>
                                <div class="author vcard">%4$s</div>',
                                esc_url(get_author_posts_url($author_id)),
                                esc_attr(sprintf(__('View all posts by %s', 'generatepress'), get_the_author())),
                                esc_html(get_the_author()),
                                $avatar_html
                            );
                            ?>
                            <?php
                            $time_string = '<span class="date-label">Published on</span><time class="entry-date published" datetime="%1$s" itemprop="datePublished">%2$s</time>';
                            if ( get_the_date() !== get_the_modified_date() ) {
                                $time_string = '<span class="date-label">Updated on</span><time class="entry-date updated-date" datetime="%3$s" itemprop="dateModified">%4$s</time>';
                            }

                            $time_string = sprintf( $time_string,
                                esc_attr( get_the_date( 'c' ) ),
                                esc_html( get_the_date() ),
                                esc_attr( get_the_modified_date( 'c' ) ),
                                esc_html( get_the_modified_date() )
                            );

                            echo sprintf( '<span class="posted-on">%s</span> ', $time_string );
                            ?>
                        </div>
                    <?php endif; ?>