Fatal error: Uncaught TypeError: call_user_func_array(): Argument #1 ($callback) must be a valid callback, cannot access protected method CatsCutomerCenter::addMainMenu() in /var/www/vhosts/cats-software.ch/httpdocs/wp-includes/class-wp-hook.php:303 Stack trace: #0 /var/www/vhosts/cats-software.ch/httpdocs/wp-includes/plugin.php(189): WP_Hook->apply_filters() #1 /var/www/vhosts/cats-software.ch/httpdocs/wp-includes/nav-menu-template.php(226): apply_filters() #2 /var/www/vhosts/cats-software.ch/httpdocs/wp-content/plugins/us-core/templates/elements/menu.php(88): wp_nav_menu() #3 /var/www/vhosts/cats-software.ch/httpdocs/wp-content/plugins/us-core/functions/helpers.php(130): include('...') #4 /var/www/vhosts/cats-software.ch/httpdocs/wp-content/plugins/us-core/functions/header.php(232): us_load_template() #5 /var/www/vhosts/cats-software.ch/httpdocs/wp-content/plugins/us-core/templates/l-header.php(77): us_output_builder_elms() #6 /var/www/vhosts/cats-software.ch/httpdocs/wp-content/plugins/us-core/functions/helpers.php(130): include('...') #7 /var/www/vhosts/cats-software.ch/httpdocs/wp-content/plugins/us-core/templates/header.php(93): us_load_template() #8 /var/www/vhosts/cats-software.ch/httpdocs/wp-content/plugins/us-core/functions/helpers.php(130): include('...') #9 /var/www/vhosts/cats-software.ch/httpdocs/wp-content/themes/Impreza/header.php(12): us_load_template() #10 /var/www/vhosts/cats-software.ch/httpdocs/wp-includes/template.php(770): require_once('...') #11 /var/www/vhosts/cats-software.ch/httpdocs/wp-includes/template.php(716): load_template() #12 /var/www/vhosts/cats-software.ch/httpdocs/wp-includes/general-template.php(48): locate_template() #13 /var/www/vhosts/cats-software.ch/httpdocs/wp-content/plugins/us-core/templates/archive.php(10): get_header() #14 /var/www/vhosts/cats-software.ch/httpdocs/wp-content/plugins/us-core/functions/helpers.php(130): include('...') #15 /var/www/vhosts/cats-software.ch/httpdocs/wp-content/plugins/us-core/templates/index.php(67): us_load_template() #16 /var/www/vhosts/cats-software.ch/httpdocs/wp-content/plugins/us-core/functions/helpers.php(130): include('...') #17 /var/www/vhosts/cats-software.ch/httpdocs/wp-content/themes/Impreza/index.php(12): us_load_template() #18 /var/www/vhosts/cats-software.ch/httpdocs/wp-includes/template-loader.php(106): include('...') #19 /var/www/vhosts/cats-software.ch/httpdocs/wp-blog-header.php(19): require_once('...') #20 /var/www/vhosts/cats-software.ch/httpdocs/index.php(17): require('...') #21 {main} thrown in /var/www/vhosts/cats-software.ch/httpdocs/wp-includes/class-wp-hook.php on line 303