I live in Hong Kong, which is a city on its own. Ideally, just "Hong Kong" should work, since it is both a city and a Special Administrative Region under China.
Nonetheless, it didn't let me sign up regardless of what I tried.
The error stated that I had to specify a city
- Hong Kong
- Hong Kong, China
<District-Name>, Hong Kong
<District-Name>, Hong Kong, China
I signed up with "San Francisco, CA, USA" just to be sure that it was my location causing the issue.
Does the profile page use a different geocoding service? I changed it to "Hong Kong" in the profile page and it worked fine, though it displays it as "Hong Kong, Hong Kong".
EDIT: The same applies to Macau as well.