Author's name is not displayed on single author's posts list

Hi,

Clicking on author’s name displays a list of all posts by the same author. In the title of the page, author’s name is not displayed. Any idea why ? It works with posts for a category.

<?php $theme->hook('content_before'); ?>
            <h2 class="page-title"><?php printf( __( 'Tous les articles de &laquo;<span>%s</span>&raquo;', 'themater' ),  get_the_author() ); ?></h2>

            <?php

Link to my site : https://www.aixlesbains.info

Thanks for any help or suggestion.