Notification button not activating

Hello,

Have just set up and installed the Plug In as it is just what a client is after.

It shows on a product page when out of stock, just as expected. The text shows on and above the button. But clicking the button has no impact.

Any ideas.

Link to product: https://cablesforcharging.com/product/type1-type-2-spring-charging-cable-32-amp-black/

Thanks
WP 4.8.2
WooCommerce 3.2.1
PHP 5.6.30