Hi, we use Twilio as a provider and this is what they have to say about delivering SMS messages to China. I know this is not specific to Twilio but rather an impact of the government regulations in place for China. Even if we did our best to try to conform to all the rules, "Twilio is currently unable to ensure that messages sent to mainland China are reliably delivered because of restrictions around content, encoding, signatures, and use case."
We decided to block those numbers as we also had a hard time maintaining monitoring stations in China before.