Fatal error: Uncaught TypeError: call_user_func(): Argument #1 ($callback) must be a valid callback, non-static method GoogleSitemapGeneratorLoader::Enable() cannot be called statically in /customers/c/3/6/markedsoptimering.dk/httpd.www/wp-includes/class-wp-hook.php:285 Stack trace: #0 /customers/c/3/6/markedsoptimering.dk/httpd.www/wp-includes/class-wp-hook.php(311): WP_Hook->apply_filters(NULL, Array) #1 /customers/c/3/6/markedsoptimering.dk/httpd.www/wp-includes/plugin.php(478): WP_Hook->do_action(Array) #2 /customers/c/3/6/markedsoptimering.dk/httpd.www/wp-settings.php(546): do_action('init') #3 /customers/c/3/6/markedsoptimering.dk/httpd.www/wp-config.php(83): require_once('/customers/c/3/...') #4 /customers/c/3/6/markedsoptimering.dk/httpd.www/wp-load.php(37): require_once('/customers/c/3/...') #5 /customers/c/3/6/markedsoptimering.dk/httpd.www/wp-blog-header.php(13): require_once('/customers/c/3/...') #6 /customers/c/3/6/markedsoptimering.dk/httpd.www/index.php(17): require('/customers/c/3/...') #7 {main} thrown in /customers/c/3/6/markedsoptimering.dk/httpd.www/wp-includes/class-wp-hook.php on line 285