WooCommerce classes are not loading on your web page. If you already added WooCommerce theme support, then you might missing WordPress body function.
Make sure you have following line in functions.php
add_theme_support( 'woocommerce' );
Also include WordPress's body function, <body>
tag must be like below.
<body <?php body_class() ?>>
If you already have any class for body, pass that class to this function like
<body <?php body_class( 'existing-class' ) ?>>
To enable WooCommerce gallery features in your theme you must declare support using add_theme_support() like so;
add_action( 'after_setup_theme', 'yourtheme_setup' );
function yourtheme_setup() {
add_theme_support( 'wc-product-gallery-zoom' );
add_theme_support( 'wc-product-gallery-lightbox' );
add_theme_support( 'wc-product-gallery-slider' );
}
More Info here