CORS issue on real device

Hello,
I’ve added proxy in ionic.config.json and also checked platform and based on my platform am changing API url but seems CORS issue is not fixed for me.

ionic.config.json

{
  "name": "eppm",
  "app_id": "",
  "type": "ionic-angular",
  "integrations": {
    "cordova": {}
  },
  "proxies": [
    {
      "path": "/path",
      "proxyUrl": "http://domain/path"
    }
  ]
}

Api-manager.ts

import { Platform } from 'ionic-angular';
@Injectable()
export class ApiManagerProvider {
url:string;
constructor(private platform: Platform, public http: HttpClient, private cManager: CookieManagerProvider) { }
 private makePostRequest(command: string, data: any) {

    if(this.platform.is('core') || this.platform.is('mobileweb')) {
      url = 'pace/rest/3.0/eppm/cmd/';
      console.log("Web");
    }
    else {
      url = 'http://vs2.paramatrix.com:8764/pace/rest/3.0/eppm/cmd/';
      console.log("Mobile");
    }

    let apiHeader = new HttpHeaders();
    let contentType = apiHeader.set('Content-Type', 'application/x-www-form-urlencoded');
    let pace = contentType.append('pace-useragent', 'rest');

    let param = new URLSearchParams();
    for (var key in data) {
      param.append(key, data[key]);
    }

    return new Promise((resolve, reject) => {
      this.http.post(this.url + command, param.toString(), { headers: pace, withCredentials: true }).subscribe(res => {
        resolve(res);
      }, (error: HttpErrorResponse) => {
        reject(error);
      });
    });
  }
}

config.xml

<access origin="*" />
<allow-intent href="http://*/*" />
<allow-intent href="https://*/*" />

Kindly help me to figure this out guys.
Thanks in advance.