Can't use GET in hololens build

[OctocatPower]

Hi everyone, I got a problem to use GET function.

I try to get a web request on my local node js server.
When i hit play in inspector, GET function work. But it don't when i make a build and deploy app on Hololens (UWP).

This is my request code used on Start (tmp is juste a debug text i use) :

RestClient.Get(baseURL + "start/holo").Then(response => {
       tmp.text = "Done";
       //EditorUtility.DisplayDialog("Response", response.Text, "Ok");
});

Did i miss something ?

Thanks for your answers.