Hello,
I have latest WP, Woocommerce and also latest version of your theme. Web is fresh out of a demo content import. When I’m trying to place an order by clicking on “Place order” button, page is loading for a while and then I get yellow error popup, except there’s no message and therefore I don’t know what the problem is supposed to be, see here https://imgur.com/a/ezC6z .
I have wp_debug and wp_script debug enabled and there are no errors displayed either. I did complete reset of my database, installed the theme again, imported all the content again and to no avail. All other plugins except required and recommended plugins are disabled.