As a follow up, I ended up calling customer service and they confirmed that China is part of the country they do not support mobile phone verification, hence they changed the option for me to receive the verification pin by email instead of SMS. Below is part of their official reply:
"I juts got an update from the Blink Team regarding the issue with verifying your Chinese phone number. Unfortunately there are lots of country codes for outside the US which are restricted to receive verification over phone and China is one of them. We can change the option for you to receiving the verification pin code over email if you want. "
Thanks everyone for help!