Partner-center-rest-api create referral

Question

Hi!

I´m trying to create a new referral (Co-Sell Opportunity) following the REST API documentation here but I always get a "Unauthorized" or "Bad request" response.
I properly get and update referrals using the same API. My sample code is:

                var request = new HttpRequestMessage(HttpMethod.Post, $"https://api.partner.microsoft.com/v1.0/engagements/referrals");  
                await this.auth.AuthenticateRequestAsync(request);  
                request.Headers.Add("client-request-id", Guid.NewGuid().ToString()); //From: https://learn.microsoft.com/en-us/partner/develop/headers  
                request.Headers.Accept.Add(new System.Net.Http.Headers.MediaTypeWithQualityHeaderValue("application/json"));  
                  
                string serializedObject = JsonConvert.SerializeObject(newReferral);  
                request.Content = new StringContent(serializedObject, Encoding.UTF8, "application/json");  
  
                log.LogInformation("[API.CreateReferral] Req Headers: " + request.Headers);  
  
                var response = await httpClient.SendAsync(request); //POST: Bad Request GET: Ok, Empty return Referral  
                response = await httpClient.PostAsync(request.RequestUri, request.Content); // POST: Unauthorized GET: Unauthorized  
  
                response.EnsureSuccessStatusCode();  
  
                using (var stream = await response.Content.ReadAsStreamAsync())  
                {  
                    createdReferral = await System.Text.Json.JsonSerializer.DeserializeAsync<Referral>(stream, serializeOptions);  
                }  

As you can see above, I tried, just for testing purposes, by SendAsync and PostAsync with different responses. I also tried to change new HttpRequestMessage(HttpMethod.Post by HttpMethod.Get just as desperation tests and I get an Ok with a empy Refererral bodu on response.

I also tried the Partener Center Store nuget SDK, but it doesn´t contains method for managing Referrals.

Any idea about what my issue could be?

Thanks in advance.

Best regards.