Most Helpful Guy
The Chinese culture is extremely subtle. You could have done (or failed to do) some random thing and that was the lynch pin. Since they don't speak English, I assume you are a Chinese speaker?
The main hangups I know of is the use of titles and gift-giving. A Chinese boy probably doesn't care about how brilliant you are as much as he cares about how sweet you are. They're typically breadwinners even if their girlfriends and wives work, so a strong career showing is unlikely to impress them.