Another way to test your "Listener" is to get the DocuSign XML response using
https://webhook.site
From there you will see the POST request with the complete XML body for your envelope.
TEST THE CREATE ENVELOPE FIRST
Before I would test my Listener, I wanted to confirm that my C# code would trigger the WebHook (via EnvelopeDefinition.EventNotification) in the DocuSign Envelope.
EnvelopeDefinition.EventNotification sets 2 lists of objects for EnvelopeEvent & RecipientEvents. Properly configuring these will fire the trigger in DocuSign Connect (Webhook).
All that was needed was to set the EventNotification.Url = the custom URL created for me on https://webhook.site
I locally ran my C# API code to create a DocuSign Envelope that would trigger the Webhook. Then I used the the DocuSign email (received moments after creating the envelope) to sign the document - which again fired the Webhook to my test listener.
GET THE XML
My properly configured code fired the DocuSign Connect (Webhook) POST event. I can see the POST request (and its XML body) on my custom URL at https://webhook.site
RESEND THE XML
Finally, copy the POST request XML sent from DocuSign and paste that XML in PostMan. Then I can locally use PostMan to "resend" that POST request (and XML body) to test my local Listener API that I am developing.