While PubNub services will operate with high availability globally, we are not able to generally guarantee access to users or systems in China because PubNub domains are occasionally blocked by China through the Great Firewall of China (GFC)

We are not able to influence how China implements its Internet blocking policies but in order to minimize the impact to your users and systems in China, the best practice is to use a custom origin for all calls to the PubNub service. 

See our article for Instructions on Requesting and Setting a Custom Origin.