Start with looking at its logs (test, prod). If you’re testing recently, the failure and error trace should be among the most recent logs. The logs will also include the input request.
Alternatively, you can gIf you want to debug a request in the code, you first need to grab the original request json.
You can go to Dialogflow History and use Raw Interaction Log
In the window that opens, copy the full text and wrap it in a top level key as “queryResult”. However, there are known differences using this way with int handling (eg passed as string here rather than an int). May be best to use the Dialogflow tester.
Reset the connection by re-configuring the tokens -