What are the main reasons for the refusal to apply for a business visa to attend the exhibition in the United States?

The main reason is that the visa officer thinks that you are not qualified for a business visa. So you need to explain to the visa officer that you are qualified, and you must be prepared to go to the visa next time. You can find an independent consultant to handle it. An independent consultant is a person with many years of experience who walks out of the organization and faces customers independently. He usually relies on many years of experience to serve customers well and is engaged in word-of-mouth business. Generally cheaper than the agency price. But because of the word-of-mouth test, it is not easy to find.