Hi @Lan Yang Greetings! Welcome to Microsoft Q&A forum. Thank you for posting this question here.
I see that you are using the latest version of Azure body tracking SDK. Instead of the latest version, can you test with the versions of unity and the SDK such as Unity Version: 2019.1.2f1 and SDK Version: Azure Kinect SDK v1.4.1 / Azure Kinect Body Tracking SDK v1.0.1 to see if that helps. Please also make sure that you copy everything in the tools folder of the body tracker sdk into the root of the unity project (same place as the assets folder).
I also found couple of old GitHub issues which got resolved by copying all the dlls from the SDK to the unity project. Here are the links to the issues
Unity BodyTracking Sample catching exception for background thread result = K4A_RESULT_FAILED
AzureKinectException: result = K4A_RESULT_FAILED
Let me know if this helps.