Sidebar widget not working in responsive site

Hi,

Wonderful theme. Great work!

I used the below code in style.css and seems not working.

@media only screen and (max-width: 991px) {
.widget-area,
.footer-widget-area {
display: block;
width: 100%;
text-align: center;
}
}

Please check the site https://www.helpingstartup.com.