Sullivan Responsiveness issues

Two responsiveness issues with the theme when I view the cart page (i.e., example.com/cart) on a mobile phone:
1. The “Update cart” button disappears and users cannot update the quantity on the cart page. For example, when customers change the quantity, they cannot click on UPDATE CART.
2. The x button to delete a product disappears on the cart page and customers cannot delete a product they have in their cart.

I cannot replicate the above issues on a PC.