Use the PutFile method to save base64 string as an attachment

I’m trying to use the PutFile method (https://help-2020r2.acumatica.com/(W(8))/Help?ScreenId=ShowWiki&pageid=591def3d-5fe5-42c1-bb35-cfe5b4c77f6f)

I am using version 23.109.0023 and here is my code:

        public async Task HandleAsync(WebhookContext context, CancellationToken cancellation)
        {
            using (var scope = GetAdminScope())
            {
                try
                {
                    if (context.Request.Method == HttpMethod.Post.Method)
                    {
                        using (var result = new JsonTextReader(context.Request.CreateTextReader()))
                        {
                            if (result.Read())
                            {
                                JsonSerializer serializer = new JsonSerializer();
                                ObjectJSON test = serializer.Deserialize<ObjectJSON>(result);

                                var bytes = Convert.FromBase64String(test.Value);
                                StreamContent contents = new StreamContent(new MemoryStream(bytes));  
                                using( RestService rs = new RestService("http://localhost", "APIUser", "********", "HBH Test", "HOJ", ""))
                                {
                                    string fileAttachResult = rs.PutFile("StockItem", "733-108", "test.txt", contents);
                                }
                            }
                        }
                    }
                    return; 
                }
                catch (Exception ex)
                {
                    return; 
                }
            }
        }

        public string PutFile(string entityName, string keys, string fileName, StreamContent file) 
        {
            try
            {
                var res = _httpClient.PutAsync(_acumaticaBaseUrl + "/entity/Default/22.200.001/" +
                    entityName + "/" + keys + "/files/" + fileName, file).Result.EnsureSuccessStatusCode();
                return res.Content.ReadAsStringAsync().Result;
            }
            catch (Exception ex) 
            {
                return ex.Message;
            }
        }

When I run the code it always goes to the catch exception with this:

System.AggregateException: One or more errors occurred. ---> System.Threading.Tasks.TaskCanceledException: A task was canceled.
   --- End of inner exception stack trace ---
   at System.Threading.Tasks.Task`1.GetResultCore(Boolean waitCompletionNotification)
   at WebhookRedList.RestService.PutFile(String entityName, String keys, String fileName, StreamContent file)
---> (Inner Exception #0) System.Threading.Tasks.TaskCanceledException: A task was canceled.<---
 

I’m not sure what I’m missing or how to get anymore information on the errors.  Any help will be much apprecieated.