Can't use font awesome in my template

Hi,

I’m coding a template fot Custom Post Type and I don’t understand why I can’t use font awesome inside instead of I put it in my post.

If I put only the <i class=”fa fa-file-pdf-o”></i> in my template it doesn’t work.
But, if I use the icon inside the post using Visual Composer, the icon appear. But what I want is just using the icon inside my template.

Take a look for the code please :

<div class="wpb_wrapper">
<?php if( get_field('fichiers_pdf_2') ):?>
" target="_blank" ><i class="fa fa-file-pdf-o"></i> <?php the_field('nom_fichier_pdf_2'); ?>
<?php endif;?>
</div>


Can you please help me?
Thanks in advance.