Error: The URL provided is not a valid Webhook URL.

Hi,

I have contact support for this error and they keep asking me to contact Enterprise Team through call. I can't call them and I am using a Developer Account which I believe should not be a problem.

Error: The URL provided is not a valid Webhook URL.

 Here's my code clearly setting the Header base on the ClientId,

[OperationContract]
			[WebInvoke(Method = "GET", RequestFormat = WebMessageFormat.Json, BodyStyle = WebMessageBodyStyle.Wrapped,
			ResponseFormat = WebMessageFormat.Json, UriTemplate = "AdobeSignNotification")]
			public string AdobeSignGetVerified()
			{
				///////
				var currentWebOperationContext = WebOperationContext.Current;
				var outgoingResponseHeaders = currentWebOperationContext.OutgoingResponse.Headers;
				var incomingRequestOrigin = currentWebOperationContext.IncomingRequest.Headers["Origin"];
				outgoingResponseHeaders.Add("Access-Control-Allow-Origin", incomingRequestOrigin);
				///////

				var headerClientId = currentWebOperationContext.IncomingRequest.Headers["X-ADOBESIGN-CLIENTID"];

				if (headerClientId != null && headerClientId.ToString() == "CB*********************5q") {
					outgoingResponseHeaders = WebOperationContext.Current.OutgoingResponse.Headers;
					outgoingResponseHeaders.Add("X-AdobeSign-ClientId", headerClientId);

					var statusCode = WebOperationContext.Current.OutgoingResponse.StatusCode;
					statusCode = System.Net.HttpStatusCode.OK;					
				}

				return string.Empty;
			}