i had the same problem as ovolatier, and I ended up adding a filter to my functions.php file, as follows:
function wpseo_title_exclude($wp_title) {
if (is_catalog_frontpage()) {
$wp_title = get_the_title().' | '.get_bloginfo('name');
return $wp_title;
}
else return $wp_title;
}
add_filter('wpseo_title','wpseo_title_exclude');
That $wp_title
line get’s the title of the current page (in this case, the name I gave the shop for the page title and base slug for products, categories & collections (Shopp Setup -> Pages)) and then appends the name I gave my site as a whole.
Hope that helps!