Ember.js empty model from REST api

I try to make a list from REST api datas.

The server give me a response like this:

{
    "data" : [
        {
          "playId" : "624a6a21-d2b4-40c4-a241-0d9660a17676",
          "title" : "Hamlet",
          "seats" : 250,
          "reservableSeats" : 200,
          "location" : "The Dysk",
          "time" : "2017-08-02T22:10:00.000+01:00",
          "readOnly" : false,
          "isCanceled" : false

        {
          "playId" : "624a6a21-d2b4-40c4-a241-0d9660a17677",
          "title" : "Hamlet2",
          "seats" : 250,
          "reservableSeats" : 180,
          "location" : "The Dysk",
          "time" : "2017-08-03T22:10:00.000+01:00",
          "readOnly" : false,
          "isCanceled" : false
        }
    ],
    "prevPage" : "http://ift.tt/2mZVF0N",
    "nextPage" : "http://ift.tt/2ndCxih",
    "objectCount" : 2
}

I have an adapter: app/adapters/application.js

import Ember from 'ember';
import DS from 'ember-data';
import JSONAPIAdapter from 'ember-data/adapters/json-api';

export default DS.JSONAPIAdapter.extend({
  namespace: 'admin/v1',
  host: `http://ift.tt/2n05KLk`,

  authManager: Ember.inject.service(),

  headers: Ember.computed('authManager.accessToken', function() {
    return {
      "X-Auth-Token": `${this.get("authManager.accessToken")}`
    };
  })
});

I want to use this model: app/models/demoplays.js

import DS from 'ember-data';

export default DS.Model.extend({
  playId: DS.attr('string'),
  title: DS.attr('string'),
  seats: DS.attr('number'),
  reservableSeats: DS.attr('number'),
  location: DS.attr('string'),
  time: DS.attr('date'),
  readOnly: DS.attr('boolean'),
  isCanceled: DS.attr('boolean')
});

I tried few serializers like RESTSerializer in app/serializers/application.js or app/serializers/demoplay.js but my models still empty.

After XHR finished loading i get two warning like this: WARNING: Encountered "objectCount" in payload, but no model was found for model name "object-count" (resolved model name using sorszamgep@serializer:demoplays:.modelNameFromPayloadKey("objectCount")).

Why my models empty?