Button in nav bar no longer working

Hi support,

I previously had a contact button in my navigation bar on my site (https://www.cleardesign.studio) but the css doesn't seem to be working anymore and the button has disappeared.

Please can you let me know what might be wrong?

Many thanks,

Stephen

All my nav bar code:

@media (min-width: 768px) {
.main-navigation .menu > .menu-item:not(.nav-button) > a::after {
content: "";
position: absolute;
right: 0;
left: 50%;
bottom: 12px;
-webkit-transform: translate3d(-50%,0,0);
transform: translate3d(-50%,0,0);

display: block;
width: 0;
height: 2px;

background-color: #c0840c;
transition: 0.5s width ease;
}
.main-navigation .menu > .menu-item.current-menu-item > a::after,
.main-navigation .menu > .menu-item.current-menu-ancestor > a::after,
.main-navigation .menu > .menu-item > a:hover::after {
width: 70%;
}
}

@media (min-width: 900px) {
.main-navigation .main-nav ul li.nav-button a {
background-color: #f5f5f5;
border: 2px solid #0c0344;
color: #0c0344;
line-height: 37px !important;
}
}
.main-navigation .main-nav ul li.nav-button:hover a {
background-color: #0c0344;
color: #ffffff;
transition: 0.3s;
}
}
@media (max-width: 900px) {
.slideout-navigation .main-nav ul li.nav-button a {
background-color: #f5f5f5;
border: 2px solid #0c0344;
color: #0c0344;
margin-top: 20px;
line-height: 50px !important;
}
}
.slideout-navigation .main-nav ul li.nav-button:hover a {
background-color: #0c0344;
color: #ffffff !important;
transition: 0.3s;
}
}