Webgl - update label text

Hi all,
i've got a problem with a WebGL project.
In this project i have a method that post some data to a webserver with a www
---------------------------------------------post data
https://xxxxxxxxx.it/web/packaging/...ht=100&lenght=1000&materials=prova&notes=nota di prova&CameraposX=10&CameraposY=10&CameraposZ=10&Cameranear=10&Camerafar=10&Camerafov=10&Imglabel=http://xxxxx.it/web/logo.png&Imggrafica=http://datafood3d.it/web/logo.png&Bgr=4&Bgg=35&Bgb=35&id=65


and then call an Unitywebrequest to download a json spool from web site after 4 seconds
---------------------------------------------------------get data
https://xxxxxx.it/web/packaging/getmodel?id=65

i transform the downloaded spool in a Object
---------------------------------------------------------write text
Modello P = JsonUtility.FromJson<Modello>(recentData);

with the P object i change the text in a label.

string Nota = P.Bgb.ToString() + " " + P.Bgg.ToString() + " " + P.Bgr.ToString();
getNoteText.text = Nota;



string web = "https://xxxxxx.it/web/packaging/addupdatemodel" + variabili;
WWW ncal = new WWW(web);
yield return ncal;
if (string.IsNullOrEmpty(ncal.error))
{
if (ncal.text != "[]")
{
Debug.Log("Inserito correttamente");
string id = getIDText.text;
StartCoroutine(Foo(id)); ///wait 4 seconds and then download datta

}
}
IEnumerator Foo(string id)
{
/
yield return new WaitForSeconds(4f); // Wait four seconds
StartCoroutine(Getmodello2(id, this.ResponseCallback)); // Download the data again
}

When i test in the editor it's all ok ....,the text in the label change correctly at every click.
When i export the WEBGL project and test in the web the project work but the label don't update immediately,i had to add a new button that only download json,create model object and after update the label text ,after some click the text update not at the first click.