How to get 3rd- and 4th-level menu items in A11Y'all to show?

I’d like to get third- and fourth-level navigation menu items to show on hover in A11Y’all.

I’ve tried adding the following to my a11yall-child theme:

div#site-navigation ul ul { display: none; position: absolute;}

div#site-navigation li li:hover > a,
div#site-navigation ul ul:hover > a,
div#site-navigation li li a:focus > a { background-color: #222; color: #ddd;}

But I’m still getting only the first and second-level menu items.