Displaying data from Ember-cli-Mirage in template - can't render retrieved record

I use a service to request data, then the service is injected into a component. Data is retrieved from Ember Mirage.

My problem is that I can't display the data as a property, even though when this property is used in computedProperty, the computedProperty correctly computes and displays.

Component template in Emblem:

.notifications-number 
each notificationService.notifications.content as |notification|
  span 

Notification service:

import Ember from 'ember';

export default Ember.Service.extend({
  store: Ember.inject.service('store'),

  // render bugs out
  notifications: function() {
    return this.get('store').findAll('notification')
  }.property(),

  // renders correctly
  countUnread: function() {
    return DS.PromiseObject.create({
      promise: this.get('notifications').then((notifications) => {
        return notifications.get('length')
      })
    });
  }.property(),
});

I have similar problem with another service and component where retrieved data is not an array but an object.

• renders <(subclass of Ember.ObjectProxy):ember404>
• renders <my-app@model:myModel::ember580:1>
• renders nothing.

Everything worked fine when I manually set values in store on app init, but doesn't work when actual asynchronous requests are sent to API mock.