Hi @marcdb,
Did you edit the template of posts?
The post title locates under this file: _content-post-header.php
Please compare and correct it:
<?php
// =============================================================================
// VIEWS/RENEW/_CONTENT-POST-HEADER.PHP
// -----------------------------------------------------------------------------
// Standard <header> output for various posts.
// =============================================================================
?>
<header class="entry-header">
<?php if ( is_single() ) : ?>
<h1 class="entry-title"><?php the_title(); ?></h1>
<?php else : ?>
<h2 class="entry-title">
<a href="<?php the_permalink(); ?>" title="<?php echo esc_attr( sprintf( __( 'Permalink to: "%s"', '__x__' ), the_title_attribute( 'echo=0' ) ) ); ?>"><?php the_title(); ?></a>
</h2>
<?php endif; ?>
<?php x_renew_entry_meta(); ?>
</header>
If you can’t do that, please change the support account to administrator so we can take a closer look.
Hope it helps 