Even though these are startups, I'm guessing that there's still an element of "guanxi" involved - i.e. the traditional personal connection dynamic of building business relationships in China.

If that is the case then just look at it as a slow burn. It can take months or even years for outsiders to properly build trust. As great as LinkedIn is, it doesn't necessarily factor in cultural differences.

I would also suggest trying to connect with some of the startup incubator communities there. I'm guessing that some of these startups are based in Shenzhen and I'm assuming there's a US Chamber of Commerce in the city (or any other major Chamber if you're not from the US). Reach out for them for guidance on the startup community. They'll have a better sense of the lay of the land there.