In dropdown.css you have the rule
.menu ul li ul {
display:none;
}
And in modxmenu.css you have the rule
#ajaxmenu li ul, #ajaxmenu li.over ul {
display:block;
}
The two rules are conflicting with each other with the second rule winning. If you change the second rule to the following it should work.
#ajaxmenu li.over ul {
display:block;
}
I’m not sure if it will cause problems elsewhere though. On a separate note, the horizontal menu doesn’t fit inside the container width when I view it, it wraps onto the next line. You need to adjust the width settings.
