.net core MVC update call API with httpclientfactory

// Here is my MVC View Controller that calls the API.
public async Task<IActionResult> UpdateAppUser(string guid)
        {
            AppUser user = new AppUser();
            HttpRequestMessage httprequest = new HttpRequestMessage(HttpMethod.Get, $"https://localhost:5001/api/account/GetUserByID/{guid}");
            // httprequest.Content = new StringContent(guid);

            var client = apiClient.CreateClient();
            var response = await client.SendAsync(httprequest);

            if (response.IsSuccessStatusCode)
            {
                var responseString = await response.Content.ReadAsStringAsync();
                user = JsonConvert.DeserializeObject<AppUser>(responseString);
               // return View("AppUser", user);
            }/**/


            return View(user);
        }
        //[Bind("FirstName,LastName,Email")]
        [HttpPost]
        [ValidateAntiForgeryToken]
        public async Task<IActionResult> UpdateAppUser(AppUser user)
        {
            if (ModelState.IsValid)
            {
                RegisterModel registerModel = new RegisterModel
                {
                    Username = user.userName,
                    FirstName = user.firstName,
                    LastName = user.lastName,
                    DateCreated = user.dateCreated,

                };
                //var model = JsonConvert.SerializeObject(user);
                var model = JsonConvert.SerializeObject(registerModel);

                HttpRequestMessage httpRequest = new HttpRequestMessage(HttpMethod.Post, $"https://localhost:5001/api/account/UpdateUser/");
                httpRequest.Content = new StringContent(model, Encoding.UTF8, "application/json");

                var client = apiClient.CreateClient();
                var response = await client.SendAsync(httpRequest);
                
                if (response.IsSuccessStatusCode)
                {
                    return View("AppUserIndex");
                }
            }
            return View(user);
        }
// Here is the API
[HttpPost("UpdateUser")]
        //[Route("UpdateUser")]
        public async Task<IActionResult> UpdateUser(RegisterModel registerModel)
        {
            if (ModelState.IsValid)
            {
                var user = await userManager.FindByEmailAsync(registerModel.Email);
                if (user != null)
                {
                    user.Email = registerModel.Email;
                    user.UserName = registerModel.Username;
                    user.FirstName = registerModel.FirstName;
                    user.LastName = registerModel.LastName;

                    IdentityResult validEmail = null;
                    if (!string.IsNullOrEmpty(registerModel.Email))
                    {
                      //  validEmail = await 
                    }

                    IdentityResult identityResult = await userManager.UpdateAsync(user);
                    if (identityResult.Succeeded)
                    {
                        return Ok();
                    }
                }
                else
                    return NotFound();
            }
            return BadRequest();
        }