Mobile device navigation menu missing

Hello!

I have scoured the website trying to find an answer through others. The navigation menu on my website has disappeared from my mobile device (works on a desktop). I have tried a couple different CSS codes I found on answers here to no avail. Please help me get this back as a website is important to our business! These are the codes that I have tried that have not worked:

@media only screen and (max-width: 768px) {
body.mobile-menu-open .overflow-wrapper {
    position: inherit !important;
}
}

@media screen and (max-width:800px) {
div#mobileMenuLink {
    display: block !important;
}
}

Can you share the website URL, page, and password (if applicable)? Thanks!