My dropdown menu on mobile devices doesn't work - html

Question

When I press the menu item on the top right side of my webpage it doesn't collapse. I have checked my code and it seems to be okay.
The website with the problem is: www.kemnet.be
I have tried putting everything in the block and made minor changes to my jquery and CSS.
I have this from a theme and added the original code to my site for testing but the dropdown still doesn't show.
<header class="navbar navbar-inverse navbar-fixed-top opaqued" role="banner">
<div class="container">
<div class="navbar-header">
<button type="button" class="navbar-toggle" data-toggle="collapse" data-target=".navbar-collapse">
<span class="sr-only">Toggle navigation</span>
<i class="fa fa-bars"></i>
</button>
<a class="bounce-in no-display animated bounceIn appear" href="index.html"></a> <img src="images\white.png">
</div>
<div class="collapse navbar-collapse">
<ul class="nav navbar-nav navbar-right">
<li class="active">Home</li>
<li>Praktisch </li>
<li>Onze Visie</li>
<li>Ons Team</li>
<li>Ons Aanbod </li>
<li>Nieuws</li>
<li>Contact</li>
<li><a class="border" href="https://www.mtc-it4.be/patient/index.html#/appointments/day/bjNkcWkyQmFRMkpDVTRFNndleFgzSlRvdC9TSU1YOXdJWklnQ2ZtMDhjcEJCYWl6RlREMWxyOGlZY2FSUk10WQ==" target="_blank">Maak een afspraak</a></li>
</ul>
</div>
</div>
</header>
I don't receive any error messages tho.

Answer 1

I just replaced <i class="fa fa-bars"></i> with classic way.
<header class="navbar navbar-inverse navbar-fixed-top opaqued" role="banner">
<div class="container">
<div class="navbar-header">
<button type="button" class="navbar-toggle" data-toggle="collapse" data-target=".navbar-collapse">
<span class="sr-only">Toggle navigation</span>
<span class="icon-bar"></span>
<span class="icon-bar"></span>
<span class="icon-bar"></span>
</button>
<a class="bounce-in no-display animated bounceIn appear" href="index.html"></a> <img src="images\white.png">
</div>
<div class="collapse navbar-collapse">
<ul class="nav navbar-nav navbar-right">
<li class="active">Home</li>
<li>Praktisch </li>
<li>Onze Visie</li>
<li>Ons Team</li>
<li>Ons Aanbod </li>
<li>Nieuws</li>
<li>Contact</li>
<li><a class="border" href="https://www.mtc-it4.be/patient/index.html#/appointments/day/bjNkcWkyQmFRMkpDVTRFNndleFgzSlRvdC9TSU1YOXdJWklnQ2ZtMDhjcEJCYWl6RlREMWxyOGlZY2FSUk10WQ==" target="_blank">Maak een afspraak</a></li>
</ul>
</div>
</div>
</header>
https://jsfiddle.net/v61aeg5r/1/