Hi,

Please try add more this code to Customize > Custom CSS to showing dropdown on mobile:

@media only screen and (max-width: 960px){
.penci-top-bar.topbar-menu{ padding-bottom: 10px; }
ul.penci-topbar-menu li:hover > ul.sub-menu, 
div.penci-topbar-menu > ul li:hover > ul.sub-menu {
    display: block;
    text-align: left;
}
ul.penci-topbar-menu li > ul.sub-menu, 
div.penci-topbar-menu > ul li > ul.sub-menu{
    text-align: left;
}
}

Best Regards,

PenciDesign