Woocommerce subscriptions do not update the cart since the last update

For reference, the site I'm working on is available here:

Home

This site offers simple products and subscription. When I add a simple product to the cart, such as a bag of coffee, the cart will update and the pop-up window "added to cart" will appear. The subscription products behaved the same way until the day I updated WordPress & WooCommerce. As you can see, adding products by subscription to the cart does not matter.
I've closed the site, exchanged the theme and disabled all the plugins, but I have the same problem on this version! Except that on the local version, the subscription products give me an error:

This site can not provide a secure connection localhost has sent an invalid response.

I've looked at the "network" section of development tools, subscription products send an XHR request called "basket /", while products that work are not. Any ideas as to why this could happen?

Is this a known bug? A bit lost as to how to move forward!