The big problem with the button

I started watching the video tutorials to create an application. There’s a man got to stick button and I have not! Tell me what could be the problem here? I can not insert a tag

That application code

<link rel="manifest" href="manifest.json">
<!-- un-comment this code to enable service worker
  if ('serviceWorker' in navigator) {
      .then(() => console.log('service worker installed'))
      .catch(err => console.log('Error', err));
<link href="lib/ionic/css/ionic.css" rel="stylesheet">
<link href="css/style.css" rel="stylesheet">
<!-- IF using Sass (run gulp sass first), then uncomment below and remove the CSS includes above
<link href="css/" rel="stylesheet">
<!-- ionic/angularjs js -->
<script src="lib/ionic/js/ionic.bundle.js"></script>
<!-- cordova script (this will be a 404 during development) -->
<script src="cordova.js"></script>
<!-- your app's js -->
<script src="js/app.js"></script>
  <ion-header-bar class="bar-positive">
    <h1 class="title">Hacker proga</h1>

<button class="button icon ion-plus>


I help somebody?I found a mistake and correct the developers!

What’s the issue? I don’t follow.

Sorry, the problem is some about the button in the navbar?

The buttons are superimposed on each other.:fearful:
Normally everything should look like this, only need to add on the top right icon.:astonished:

Button does not want to be added to the header!