How to retrieve Firebase "remote config" with Cordova

I'm trying to use the plugin cordova-plugin-firebase for retrieving Firebase Remote Configs, but value is always null.

Has anyone gotten this to work, or see something wrong in my implementation?

Thanks.

$ionicPlatform.ready(function () {
   if (window.FirebasePlugin) {
      window.FirebasePlugin.getValue("xxx", function (value) {
         console.log(value);
      }, function (error) {
         console.error(error);
      });
   }
});

Environment

Cordova CLI: 7.0.1 Gulp version: CLI version 1.2.1 Gulp local: Local version 3.9.1 Ionic Framework Version: 1.3.2 Ionic CLI Version: 2.1.1 Ionic App Lib Version: 2.1.1 ios-deploy version: 1.9.1 ios-sim version: 5.0.6 OS: Mac OS X Sierra Node Version: v4.4.0 Xcode version: Xcode 8.3.1 Build version 8E1000a