Get request not work in android

my app does not work anymore. in ionic 3 it worked, now with ionic 4 is occurring error in the request.
The get request does not enter the server.
My function on the server:
public function test_app ( username = null, key = null) {
header (“Access-Control-Allow-Origin: *”);
header (“Access-Control-Allow-Headers: *”);
json = '{"a": 1, "b": 2, "c": 3, "d": 4, "e": 5}'; return json;


return new Promise ((resolve, reject) => {
let url = this.API_URL + ‘/ test_app’;
this.http.get (url).subscribe ((result: any) => {
resolves (result.json ());
(error) => {
reject (error.json ());

In the browser (ionic serve) is working normally, android does not work

help me please?

What are your server URLs? Is your server hosted or you are testing from localhost? If the latter is the case, is server and mobile both on same network?

Is your server hosted or testing from localhost? : server hosted
If the latter is the case, is the server and mobile both on the same network? No

I installed the postman on the mobile and the request worked, I do not know if I need to do something on my serve

Ok, it’s hard to say anything without looking at the errors. Best way to debug this is to install the app on android, enable USB debugging, attach it to the PC and debug it from chrome console.