The menu is not pressed on the mobile version - how to fix it?

Question

HTML

There is a site on WordPress'e - buhgkh.ru
On mobile versions the menu button is not pressed. How could this be corrected? The button does not respond both on the computer and on smartphones.

Answer 1

The styles are:

@media screen and (max-width: 768px)
.main-navigation ul {
    display: none;
}

Accordingly, the menu is hidden, and there is no js function to add a class to open on click.