Google structured data > hentry (missing author) failure & modified signal

Hi support team,

I am having the issue, that google webmaster delivers me errors in case of
Structured Data > hentry (markup: microformats.org) > missing author

Please help me to solve this issue may by adding some code into the child theme fundtions.php to enable the author and modified data.

Find here an article which shall be may helpful

//add hatom data
function add_suf_hatom_data($content) {
    $t = get_the_modified_time('F jS, Y');
    $author = get_the_author();
    $title = get_the_title();
if (is_home() || is_singular() || is_archive() ) {
        $content .= '<div class="hatom-extra" style="display:none;visibility:hidden;"><span class="entry-title">'.$title.'</span> was last modified: <span class="updated"> '.$t.'</span> by <span class="author vcard"><span class="fn">'.$author.'</span></span></div>';
    }
    return $content;
    }
add_filter('the_content', 'add_suf_hatom_data');

Please help me to solve the google structured data error problem.

Thanks, Alex