So, when u r on mobile, at the first open, the categories dropdown menu works fine, but after you click on some category to navigate, you are not able to see the dropdown anymore. So, the dropdown works only the first time, after u navigate to a category from the categories into the shop title, the dropdown is not there anymore.
Go and try it. Go to vino-meze.com/shop and open the categories title menu, navigate to a category and open the categories menu again. You will see that the drop down is not there anymore.