application-error is workingbut not the error is working.

controllers.application.js

import Controller from 'ember-controller';

export default Controller.extend({
  init() {
    this._super(...arguments);
    console.log('application controller initialised');
  }
});

controllers.error.js

import Controller from 'ember-controller';

export default Controller.extend({
  init() {
    this._super(...arguments);
    console.log('error controller initialised');
  }
});

controllers.loading.js

import Controller from 'ember-controller';

export default Controller.extend({
  init() {
    this._super(...arguments);
    console.log('loading controller initialised');
  }
});

routes.application.js

import Route from 'ember-route';
import RSVP from 'rsvp';
import { later } from 'ember-runloop';

export default Route.extend({
  model() {
    return new RSVP.Promise((resolve, reject) => {
      later(() => {
        reject(
          new Error('failed to load application model')
        );
        // resolve();
      }, 500);
    });
  },
  
  actions: {
    loading() {
      console.log('application loading action'); 
      return true;
    },
    
    error() {
      console.log('application error action');
      return true;
    }
  }
});

routes.error.js

import Route from 'ember-route';

export default Route.extend({
  activate() {
    console.log('error route activated');
  }
}); 

routes.loading.js

import Route from 'ember-route';

export default Route.extend({
  activate() {
    console.log('loading route activated ');
  }
}); 

styles.app.css

:root {
  padding: 15px; 
}

:root::before {
  content: "If you don't see anything here (apart from this message), then the Ember app produced a white screen of death :(";
}

templates.application-error.hbs

application errorhbs

templates.application-loading.hbs

application loading 

templates.application.hbs

Application template

templates.error.hbs

Error template 

templates.loading.hbs

Loading template

twiddle.json

{
  "version": "0.10.5",
  "EmberENV": {
    "FEATURES": {}
  },
  "options": {
    "use_pods": false,
    "enable-testing": false
  },
  "dependencies": {
    "jquery": "https://cdnjs.cloudflare.com/ajax/libs/jquery/1.11.3/jquery.js",
    "ember": "2.8.0",
    "ember-data": "2.8.0",
    "ember-template-compiler": "2.8.0",
    "ember-testing": "2.8.0"
  },
  "addons": {}
}