Google does not index breadcrumb navigation
<p>I would like to ask for help.
5 months ago, I added this code on my web:</p>

<pre><code>&lt;script type="application/ld+json"&gt;
    {
    "@context": "http://myweb.com",
    "@type": "BreadcrumbList",
    "itemListElement":
    [
    {
    "@type": "ListItem",
    "position": 1,
    "item":
    {
    "@id": "http://myweb.com",
    "name": "Myweb"
    }
    }
                ,{
        "@type": "ListItem",
        "position": 2,
        "item":
        {
        "@id": "http://myweb.com/adverts/cars",
        "name": "Cars"
        }
        }
                    ]
    }
&lt;/script&gt;
</code></pre>

<p>But Google is still not showing breadcrumb navigation by results on my web. Where am I wrong?
Thanks everyone.</p>