If the logo is no longer displayed after a Gambio update, this may be due to a change in the variable declaration. This is defined in the file \templates\YOUR_TEMPLATE\source\boxes\gm_logo.php. In older templates, this is done using the variable $gm_logo.
This variable is no longer populated in the new standard template (Honeygrid). It is sufficient to populate $gm_logo again in the file mentioned above, for example with the following line:
$this->set_content_data('gm_logo', '<a href="' . xtc_href_link(FILENAME_DEFAULT, '', 'NONSSL') . '">' . $logoManager->get_logo() . '</a>');
This will make the logo appear again.
