How can I see the attached parameters and headers in Fiddler?

I have the following code (Core 3.1 in VS2019):

                var client = new RestClient(url);

                ServicePointManager.Expect100Continue = true;
                ServicePointManager.DefaultConnectionLimit = 9999;
                ServicePointManager.SecurityProtocol = SecurityProtocolType.Tls12;

                // Add certificate
                var certFile = Path.Combine(certificateFolder, certificateFile);
                X509Certificate2 certificate = new X509Certificate2(certFile, certificatePassword);
                client.ClientCertificates = new X509CertificateCollection() { certificate };

                // Set web proxy
               // client.Proxy = new WebProxy(proxyUrl, proxyPort) { BypassProxyOnLocal = false };
                client.Proxy = new WebProxy("127.0.0.1", 8888);

                // Create request; add headers and parameters
                var request = new RestRequest(Method.POST);
                request.AddParameter("Authorization", authorization, ParameterType.HttpHeader);
                request.AddParameter("Content-Type", "application/x-www-form-urlencoded", ParameterType.HttpHeader);
                request.AddParameter("grant_type", "client_cert");
                request.AddParameter("scope", "openid");
                IRestResponse response = client.Execute(request);

                if (!response.IsSuccessful || response.StatusCode != HttpStatusCode.OK || response.ErrorException != null)
                {
                    throw new Exception("Unexpected response.");
                }

                System.Diagnostics.Debug.WriteLine(response);

I have the proxy set to local host so that I can capture what is happening in Fiddler.

In Fiddler it is showing the following error:

fiddler.network.https> HTTPS handshake to myApiEndpointUrl (for #25) failed. System.Security.Authentication.AuthenticationException A call to SSPI failed, see inner exception. < The message received was unexpected or badly formatted

Win32 (SChannel) Native Error Code: 0x80090326

When I look at the Headers tab (in Fiddler) all it shows is:

Response Headers
HTTP/1.1 200 Connection established

The other tabs show similar or nothing.

Questions: 1. How can I view what is actually being sent, in other words, are the headers and parameters not being attached correctly? 2. Even when I look at the value of request in debug mode at the time of execution it doesn't provide me with a way of seeing the headers/parameters.

Thanks,