Add to cart button issue

Hello.

I am having an issue since upgrading to 1.4.2. The "Add to Cart" button only works when I have the "After a product is added to the cart" setting set to "Always go to the checkout". However, I would prefer to use the "Stay and display a popup notice".

Any ideas how I can fix this please guys?

Could you tell us what is the problem you're having ?
On our end, the add to cart button works with all the values of the "After a product is added to the cart" setting. You can test on our demo website where we use "Stay and display a popup notice" and it's working fine.