Http receive 415 status code

В чем причина 415 ответа сервера?

клиент:

 public async Task<bool> AddUser(User user)
 {// https://localhost:7274/RabbitMq/AddUser
     using HttpClient client = httpClientFactory.CreateClient();
         //client.BaseAddress = new Uri(baseUrl);
         using var content = new MultipartFormDataContent();
         var json = JsonConvert.SerializeObject(user);
         var userContent = new StringContent(json, Encoding.UTF8, "application/json");
         //userContent.Headers.ContentDisposition = new ContentDispositionHeaderValue("form-data")
         //{
         //    Name = "info"
         //};

         content.Add(userContent);
         var response = await client.PostAsync("https://localhost:7274/RabbitMq/AddUser", content);

         return response.IsSuccessStatusCode;
     
     return false;
 }

сервер:

        [HttpPost]
        [Microsoft.AspNetCore.Mvc.Route("AddUser")]
        public async Task<IActionResult> AddUser(User user) // public IActionResult AddUser(User user)
        {
            Debug.WriteLine($"Получен запрос на добавление пользователя");
            _mqService.AddUser(user);

            return   Ok("User send");
        }