Visa denied

I and a friend got an invitation from our business partners in Zhang Zhou, Hunan Province. We made all the documents required and attended the interview successfully. We were told to come back for our visa 10 days later, but when we reported back we discovered that the visa had been denied without any explanation.

When we contacted the business partner in China he told us that we were not the only one. The company had also invited another person from Turkey but his visa had been denied. What do you think could be the problem and what can we do to get to China because we have an urgent business need to be there.

Thanks