You mean, when you click the checkout button in the left column of the page, it works? I have the issue on two different machines in two different browsers. Very strange.
I suppose you mean I should set the cart notify plugin to add to cart button? In fact, it doesn't matter what I do in that plugin, it makes no difference. Neither display location nor display position nor autohide delay change in frontend when I make the changes in the plugin, not even with a hard refresh. I've managed to extend the autohide in configurations, that's a workaround. But if you could let me know where, other than in the plugin, I need to change to the new add to cart system, that would be greatly appreciated. (I found information on that functionality itself but not on how to activate it.)