Flickity-fade slider not working after following the installation docs from github; flickity just run like the regular slider

I'm following this flickity slide fade docs FlickityFade Installation

Here is the css cdn package

<link rel="stylesheet" href="https://unpkg.com/flickity@2/dist/flickity.min.css">
<link rel="stylesheet" href="https://unpkg.com/flickity-fade@2/flickity-fade.css">

Here is the carousel html and the script set up

<div class="testimonial-carousel">
     ....carousels div....
</div>

<script src="https://unpkg.com/flickity@2/dist/flickity.pkgd.min.js"></script>
<script src="https://unpkg.com/flickity-fade@2/flickity-fade.js"></script>
<script>
    $('.testimonial-carousel').flickity({
        // options
        fade: true,
        cellAlign: 'left',
        contain: true,
        prevNextButtons: false
    });
</script>

i don't figure out why this slide fade not working, only run in the dom like i am using normal flickity package but, it shown error like link below

Error screenshot from my console log

Found the solution here Flickity issues