Web API Put Request generates an Http 405 Method Not Allowed error

Here's the call to the PUT method on my Web API - the third line in the method (I am calling the Web API from an ASP.NET MVC front end):

https://i.stack.imgur.com/V9aat.jpg

client.BaseAddress is http://localhost/CallCOPAPI/.

Here's contactUri:

https://i.stack.imgur.com/VsuVL.jpg

Here's contactUri.PathAndQuery:

https://i.stack.imgur.com/Vd8bT.jpg

And finally, here's my 405 response:

https://i.stack.imgur.com/VtCX4.jpg

Here's the WebApi.config in my Web API project:

        public static void Register(HttpConfiguration config)
        {
            config.Routes.MapHttpRoute(
                name: "DefaultApi",
                routeTemplate: "api/{controller}/{id}",
                defaults: new { id = RouteParameter.Optional }
            );

            config.Routes.MapHttpRoute(
                name: "DefaultApiGet",
                routeTemplate: "api/{controller}/{action}/{regionId}",
                defaults: new { action = "Get" },
                constraints: new { httpMethod = new HttpMethodConstraint("GET") });

            var json = config.Formatters.JsonFormatter;
            json.SerializerSettings.PreserveReferencesHandling = Newtonsoft.Json.PreserveReferencesHandling.Objects;
            config.Formatters.Remove(config.Formatters.XmlFormatter);

I've tried stripping down the path that gets passed into PutAsJsonAsync to string.Format("/api/department/{0}", department.Id) and string.Format("http://localhost/CallCOPAPI/api/department/{0}", department.Id) with no luck.

Does anyone have any ideas why I'm getting the 405 error?

UPDATE

As per request, here's my Department controller code (I will post both the Department controller code for my front end project, as well as the Department ApiController code for the WebAPI):

Front End Department Controller

namespace CallCOP.Controllers
{
    public class DepartmentController : Controller
    {
        HttpClient client = new HttpClient();
        HttpResponseMessage response = new HttpResponseMessage();
        Uri contactUri = null;

        public DepartmentController()
        {
            // set base address of WebAPI depending on your current environment
            client.BaseAddress = new Uri(ConfigurationManager.AppSettings[string.Format("APIEnvBaseAddress-{0}", CallCOP.Helpers.ConfigHelper.COPApplEnv)]);

            // Add an Accept header for JSON format.
            client.DefaultRequestHeaders.Accept.Add(
                new MediaTypeWithQualityHeaderValue("application/json"));
        }

        // need to only get departments that correspond to a Contact ID.
        // GET: /Department/?regionId={0}
        public ActionResult Index(int regionId)
        {
            response = client.GetAsync(string.Format("api/department/GetDeptsByRegionId/{0}", regionId)).Result;
            if (response.IsSuccessStatusCode)
            {
                var departments = response.Content.ReadAsAsync<IEnumerable<Department>>().Result;
                return View(departments);
            }
            else
            {
                LoggerHelper.GetLogger().InsertError(new Exception(string.Format(
                    "Cannot retrieve the list of department records due to HTTP Response Status Code not being successful: {0}", response.StatusCode)));
                return RedirectToAction("Index");
            }

        }

        //
        // GET: /Department/Create

        public ActionResult Create(int regionId)
        {
            return View();
        }

        //
        // POST: /Department/Create
        [HttpPost]
        [ValidateAntiForgeryToken]
        public ActionResult Create(int regionId, Department department)
        {
            department.RegionId = regionId;
            response = client.PostAsJsonAsync("api/department", department).Result;
            if (response.IsSuccessStatusCode)
            {
                return RedirectToAction("Edit", "Region", new { id = regionId });
            }
            else
            {
                LoggerHelper.GetLogger().InsertError(new Exception(string.Format(
                    "Cannot create a new department due to HTTP Response Status Code not being successful: {0}", response.StatusCode)));
                return RedirectToAction("Edit", "Region", new { id = regionId });
            }
        }

        //
        // GET: /Department/Edit/5

        public ActionResult Edit(int id = 0)
        {
            response = client.GetAsync(string.Format("api/department/{0}", id)).Result;
            Department department = response.Content.ReadAsAsync<Department>().Result;
            if (department == null)
            {
                return HttpNotFound();
            }
            return View(department);
        }

        //
        // POST: /Department/Edit/5

        [HttpPost]
        [ValidateAntiForgeryToken]
        public ActionResult Edit(int regionId, Department department)
        {
            response = client.GetAsync(string.Format("api/department/{0}", department.Id)).Result;
            contactUri = response.RequestMessage.RequestUri;
            response = client.PutAsJsonAsync(string.Format(contactUri.PathAndQuery), department).Result;
            if (response.IsSuccessStatusCode)
            {
                return RedirectToAction("Index", new { regionId = regionId });
            }
            else
            {
                LoggerHelper.GetLogger().InsertError(new Exception(string.Format(
                    "Cannot edit the department record due to HTTP Response Status Code not being successful: {0}", response.StatusCode)));
                return RedirectToAction("Index", new { regionId = regionId });
            }
        }

        //
        // GET: /Department/Delete/5

        public ActionResult Delete(int id = 0)
        {
            response = client.GetAsync(string.Format("api/department/{0}", id)).Result;
            Department department = response.Content.ReadAsAsync<Department>().Result;

            if (department == null)
            {
                return HttpNotFound();
            }
            return View(department);
        }

        //
        // POST: /Department/Delete/5

        [HttpPost, ActionName("Delete")]
        [ValidateAntiForgeryToken]
        public ActionResult DeleteConfirmed(int regionId, int id)
        {
            response = client.GetAsync(string.Format("api/department/{0}", id)).Result;
            contactUri = response.RequestMessage.RequestUri;
            response = client.DeleteAsync(contactUri).Result;
            return RedirectToAction("Index", new { regionId = regionId });
        }
    }
}

Web API Department ApiController

namespace CallCOPAPI.Controllers
{
    public class DepartmentController : ApiController
    {
        private CallCOPEntities db = new CallCOPEntities(HelperClasses.DBHelper.GetConnectionString());

        // GET api/department
        public IEnumerable<Department> Get()
        {
            return db.Departments.AsEnumerable();
        }

        // GET api/department/5
        public Department Get(int id)
        {
            Department dept = db.Departments.Find(id);
            if (dept == null)
            {
                throw new HttpResponseException(Request.CreateResponse(HttpStatusCode.NotFound));
            }

            return dept;
        }

        // this should accept a contact id and return departments related to the particular contact record
        // GET api/department/5
        public IEnumerable<Department> GetDeptsByRegionId(int regionId)
        {
            IEnumerable<Department> depts = (from i in db.Departments
                                             where i.RegionId == regionId 
                                             select i);
            return depts;
        }

        // POST api/department
        public HttpResponseMessage Post(Department department)
        {
            if (ModelState.IsValid)
            {
                db.Departments.Add(department);
                db.SaveChanges();

                HttpResponseMessage response = Request.CreateResponse(HttpStatusCode.Created, department);
                return response;
            }
            else
            {
                return Request.CreateErrorResponse(HttpStatusCode.BadRequest, ModelState);
            }
        }

        // PUT api/department/5
        public HttpResponseMessage Put(int id, Department department)
        {
            if (!ModelState.IsValid)
            {
                return Request.CreateErrorResponse(HttpStatusCode.BadRequest, ModelState);
            }

            if (id != department.Id)
            {
                return Request.CreateResponse(HttpStatusCode.BadRequest);
            }

            db.Entry(department).State = EntityState.Modified;

            try
            {
                db.SaveChanges();
            }
            catch (DbUpdateConcurrencyException ex)
            {
                return Request.CreateErrorResponse(HttpStatusCode.NotFound, ex);
            }

            return Request.CreateResponse(HttpStatusCode.OK);
        }

        // DELETE api/department/5
        public HttpResponseMessage Delete(int id)
        {
            Department department = db.Departments.Find(id);
            if (department == null)
            {
                return Request.CreateResponse(HttpStatusCode.NotFound);
            }

            db.Departments.Remove(department);

            try
            {
                db.SaveChanges();
            }
            catch (DbUpdateConcurrencyException ex)
            {
                return Request.CreateErrorResponse(HttpStatusCode.NotFound, ex);
            }

            return Request.CreateResponse(HttpStatusCode.OK, department);
        }
    }
}