postasync submitting content null

I'm in a Xamarin project where I use a web service in PHP.

The problem is as follows, I send json to ws but when I receive it by POST, nothing arrives on it

C # code:

           HttpContent content = new StringContent(json, Encoding.UTF8, "application/json");

            using (var client = new HttpClient()) {
                client.BaseAddress = uri;

                client.DefaultRequestHeaders.Accept.Clear();
                client.DefaultRequestHeaders.Accept.Add(new MediaTypeWithQualityHeaderValue("application/json"));
                HttpResponseMessage response = client.PostAsync(uriActionString, content).Result;
                if (response.StatusCode == HttpStatusCode.BadRequest) {
                    ret = false;
                }

                return ret;
            }

obs: I already changed the client.PostAsync(...).Result; for

 await client.PostAsync(...);

and without result.

By analyzing the application's performance, I can see both sides, and at first glance, it's "okay."

• comments:

Whengivingprint_rin$_POST,anemptyarrayisarriving.

Thevariable"json" that is in the StringContent is arriving correctly in the method.

The url is set correctly. When testing the same url and sending a variable by POST in postman, it is returning correctly as well.

As this is a more complex json, in this case I can not use the FormUrlEncodedContent object