Hello,

Your issue has been solved. I have deactivated all the 3rd party plugins from the site and activate only theme-required plugins on the site, now the add to cart button is working fine, and adding the product in the cart, please see the screenshot: https://ibb.co/wd04g9q

Now, please activate the 3rd party plugins one by one and check which plugin is creating the issue for you.

Best Regards.