Add to Cart not working

Hello, i have the PREMIUM version of your plugin and I would like to use it for 3-5 other shops. Before I can do that I need to solve an issue with your plugin. When I click on the “add to cart” button on the product overview: https://www.medihaus.de/vollgesichtsmasken/ it doesnt add the product into the floating cart.

Do you have an idea how to fix that?

thank you,
Hannes

The page I need help with: [log in to see the link]