I fixed it myselft, by changing the funtions-enfold.php. Due to the fact that we are using Zen Menu Logic the theme_location is not set to “avia” but the function is looking for this to add the search icon. So I have added this.

function avia_append_search_nav ( $items, $args )
{
if(avia_get_option(‘header_searchicon’,’header_searchicon’) != “header_searchicon”) return $items;
if(avia_get_option(‘header_position’, ‘header_top’) != “header_top”) return $items;

if ((is_object($args) && $args->theme_location == ” or $args->theme_location == ‘avia’ ) || (is_string($args) && $args = “fallback_menu”))
{
global $avia_config;
ob_start();
get_search_form();
$form = htmlspecialchars(ob_get_clean()) ;

$items .= ‘<li id=”menu-item-search” class=”noMobile menu-item menu-item-search-dropdown menu-item-avia-special”>
<span class=”avia_hidden_link_text”>’.__(‘Search’,’avia_framework’).'</span>
‘;
}
return $items;