Chinese consulates in the United States have been tightening their enforcement of visa requirements.
A recent announcement from the Chinese consulate in Hong Kong stated that as a policy matter, applicants who are not residents of Hong Kong should apply for a Chinese visa from their home countries. Foreign national applicants at the Hong Kong consulate must provide their Hong Kong permanent residence card or work permit. This policy change is in line with the Chinese government's ongoing effort to crack down on unlawful employment of foreign nationals in China. In particular, this new policy will make it more difficult for foreign nationals who work in mainland China on an F business visitor visa to travel to Hong Kong every few months to satisfy the length-of-stay requirement of their visas, or to renew their F visas and re-enter mainland China.