Messages to China require use case vetting, please refer to this support article https://support.twilio.com/hc/en-us/articles/17024185400859-Use-Case-Vetting-for-Verify-Messages-to-China to understand this in detail.
HTTP status: 400
Your account is not allowed to create verifications towards China
Please read this support article https://support.twilio.com/hc/en-us/articles/17024185400859-Use-Case-Vetting-for-Verify-Messages-to-China to get your more details on how to get your use case vetted for China.