From their website: The Google Maps APIs are served within China from http://maps.google.cn. When serving content to China, replace https://maps.googleapis.com  with http://maps.google.cn.

The maps.googleapis.com is set in libs/css_js_include_helper.php

Go on  libs/css_js_include_helper.php and replace  https://maps-api-ssl.google.com   with      https://maps.google.cn