Ask HN: How to get our money back from client

We are career coaches specializing in programming, and we typically charge our fees after services are finished. Unfortunately, we've encountered an issue where a client, who enrolled in our course, became unresponsive six months into the program. We have his full name, contact details, employer's information, and his resume. However, since he is from Taiwan, his information isn't adequate for us to file a legal claim in the United States. We've attempted to reach out to his employer with a formal complaint but have not received any acknowledgment or reply. I don’t know if anyone has similar experience in getting back the money.