How to POST JsonObject with Retrofit 2?

Question

In my app I'm creating a JsonObject

JSONObject jsonObject = new JSONObject();
            jsonObject.put("command", "session.intSessOK");
            jsonObject.put("appToken", appToken);
            jsonObject.put("aesIv", aesIv2Encrypted);
            jsonObject.put("nextToken", nextToken);

putting values in it

        byte[] body = Base64.encode(jsonObject.toString().getBytes("UTF-8"), Base64.NO_WRAP);
        AesUtil aesUtil = new AesUtil(aesKeyIv.getKey(), aesKeyIv.getInitVector());
        String finalBody = aesUtil.encrypt(body);

converting it to base64 and encrypting it

    JSONObject jsonObjectFinal = new JSONObject();
jsonObjectFinal.put("dt", finalBody);

finally creating another json object and send the encrypted body as "dt" value

 sendInitOk(jsonObjectFinal);

And then:

private void sendInitOk(JSONObject jsonObject) {

        apiService.generic(jsonObject).enqueue(new Callback<GenericWrapper>() {


            @Override
            public void onResponse(Call<GenericWrapper> call, Response<GenericWrapper> response) {
                ApiServiceSingleton.getInstance().setHeaders(response.headers());
                Timber.d("INIT SESSION OK: " + response.body().toString());
                try {
                    Aes aes = new Aes();
                    ApiServiceSingleton apiSingleton = ApiServiceSingleton.getInstance();
                    byte[] dataBytes = Base64.decode(response.body().getDt(), Base64.NO_WRAP);
                    byte[] data = aes.decrypt(apiSingleton.getIv().getBytes("UTF-8"), apiSingleton.getKey().getBytes(), dataBytes);
                    String dataString = new String(data);
                    Timber.d(dataString);

                } catch (Exception ignored) {
                    ignored.printStackTrace();
                }
            }

            @Override
            public void onFailure(Call<GenericWrapper> call, Throwable t) {
                Timber.e("INIT SESSION OK ERROR" + t.getMessage());
            }

        });


    }

Api service:

@POST("getRequest")
    Call<GenericWrapper> generic(@Body JSONObject jsonObject);

GenericWrapper class in kotlin:

class GenericWrapper {

    @SerializedName("dt")
    @Expose
    var dt: String? = null

}

There is no error in client side but I'm not getting a response.

Backend side gets the json value as NameValuePairs = { "dt" = "......."

instead of "dt" = ...

edit: so I used this answer and switched to Gson's JsonObject but this time I'm getting a BadPaddingException. Strange NameValuePairs thing dissepeared thpough