PutAsync doesn't send request to web api, but fiddler works fine

I have been trying to figure out what is going wrong for a few hours now and i just can't find what is going wrong.

Via the Mvc application the put method doesn't get hit, the request doesn't happen. But when i test it in fiddler the PutMethod in the api works.

Hopefully someone can clear things up for me.

Also pointers for a better structure or some good documentation are welcome .

    public void UpdateWerknemerCompetentieDetail(int wnID, int WNC, CompetentieWerknemerDetail detail)
    {
        using (HttpClient client = new HttpClient())
        {
            string token = (string)HttpContext.Current.Session["token"];
            client.DefaultRequestHeaders.Authorization = new AuthenticationHeaderValue("Bearer", token);
            var wn = GetWerknemerById(wnID);
            //var wnc = wn.CompetentiesWerknemer.Select(c => c).Where(c => c.ID == WNC).FirstOrDefault();
            detail.CompetentieWerknemerID = WNC;
            //wnc.CompetentieWerknemerDetail = detail;
            var url = String.Format(URL + "PutDetails?id=" + WNC);
             var json = JsonConvert.SerializeObject(detail, new JsonSerializerSettings()
             {
                 ReferenceLoopHandling = Newtonsoft.Json.ReferenceLoopHandling.Ignore
             });         
            var response =  client.PutAsync(url, new StringContent(json, Encoding.UTF8, "application/json"));

        }
    }

The above code is my service that should make the request to the api.

Here is the web api IHttpActionResult method (the put method).

    [Route("PutDetails")]
    [HttpPut]
    public IHttpActionResult PutWerknemerCompetentieDetails(int id, [FromBody]CompetentieWerknemerDetail cwn)
    {
        if (!ModelState.IsValid)
        {
            return BadRequest(ModelState);
        }

        if (id != cwn.CompetentieWerknemerID)
        {
            return BadRequest();
        }

        //_db.Entry(cwn).State = EntityState.Modified;

        try
        {
            _db.CompetentieWerknemerDetail.Add(cwn);
            _db.SaveChanges();
        }
        catch (DbUpdateConcurrencyException)
        {
            if (!WerknemerExist(id))
            {
                return NotFound();
            }
            else
            {
                throw;
            }
        }

        return StatusCode(HttpStatusCode.NoContent);
    }