Error after the installation

After installing wordbooker I got this in Wordbooker Settings

Notices

Your PHP install is missing simplexml_load_string()

Fatal error: Uncaught exception ‘Exception’ with message ‘Нет ни одного доступного HTTP-транспорта, который может завершить запрос.’ in /home/autogen/svoekino.com/docs/wp-content/plugins/wordbooker/includes/wordbooker_facebook_wp_http.php:268 Stack trace: #0 /home/autogen/svoekino.com/docs/wp-content/plugins/wordbooker/includes/wordbooker_facebook_wp_http.php(168): wordbooker_make_http_call2(‘https://wordboo…’) #1 /home/autogen/svoekino.com/docs/wp-content/plugins/wordbooker/includes/wordbooker_cron.php(24): wordbooker_check_version() #2 /home/autogen/svoekino.com/docs/wp-content/plugins/wordbooker/includes/wordbooker_options.php(216): wordbooker_cache_refresh(1) #3 [internal function]: wordbooker_option_manager(”) #4 /home/autogen/svoekino.com/docs/wp-includes/plugin.php(470): call_user_func_array(‘wordbooker_opti…’, Array) #5 /home/autogen/svoekino.com/docs/wp-admin/admin.php(211): do_action(‘settings_page_w…’) #6 /home/autogen/svoekino.com/docs/wp-admin/o in /home/autogen/svoekino.com/docs/wp-content/plugins/wordbooker/includes/wordbooker_facebook_wp_http.php on line 268

What can it be? Can you help me please?

https://www.ads-software.com/plugins/wordbooker/