Bulma.io fullheight hero background - html

Question

Trying to add background image to bulma.io hero section, but it doesn't work!
Heres the code:
<div>
<section class="hero is-primary is-fullheight header-image">
<!-- Hero header: will stick at the top -->
<div class="hero-head">
<header class="navbar">
<div class="navbar-brand">
<a class="navbar-item" href="http://bulma.io">
<img src="http://bulma.io/images/bulma-logo.png" alt="Bulma: a modern CSS framework based on Flexbox" width="112" height="28">
</a>
<div class="navbar-burger" v-on:click="showNav = !showNav" v-bind:class="{ 'is-active' : showNav }">
<span></span>
<span></span>
<span></span>
</div>
</div>
<div class="navbar-menu" v-bind:class="{ 'is-active' : showNav }">
<!-- navbar start, navbar end -->
<div class="navbar-end">
<a class="navbar-item" href="/about">About</a>
<a class="navbar-item" href="/path">Path</a>
<a class="navbar-item" href="/blog">Blog</a>
</div>
</div>
</header>
</div>
<!-- Hero content: will be in the middle -->
<div class="hero-body">
<div class="container has-text-centered">
<h1 class="title">
Title
</h1>
<h2 class="subtitle">
Subtitle
</h2>
</div>
</div>
<!-- Hero footer: will stick at the bottom -->
<div class="hero-foot">
<nav class="tabs is-boxed is-fullwidth">
<div class="container">
<ul>
<li class="is-active"><a>Overview</a></li>
<li><a>Modifiers</a></li>
<li><a>Grid</a></li>
<li><a>Elements</a></li>
<li><a>Components</a></li>
<li><a>Layout</a></li>
</ul>
</div>
</nav>
</div>
</section>
</div>
And css code:
.header-image {
background-image: url("http://orig14.deviantart.net/7584/f/2015/181/2/7/flat_mountains_landscape_by_ggiuliafilippini-d8zdbco.jpg");
background-position: center center;
background-repeat: no-repeat;
background-attachment: fixed;
background-size: cover;
background-color: #999;
}
Theres the question, why this won't work?
Everything should work as expected, there is also another one post on stackowerflow about this question, but the solution from that post also won't work!

Answer 1

Your code works as expected on my local environment.
The most probable reason your code is not working is because you forgot or didn't link Bulma correctly in the header.