Help with burger menu on IOS

I have recently made a site live and the burger menu works fine on android phones but not on IOS.

I have used some code so that the burger menu stays on desktop which I think may be causing the issue, any ideas?

site here

Thanks!

Code below:

.header-burger { display:flex!important}
.header--menu-open .header-menu {opacity: 1!important;visibility: visible!important;}
.header-nav,  {visibility:hidden!important}
.header-burger {position: absolute;}

.header-title-logo { 
    text-align:center;
    margin-left:0%;
}

/* Hide overlay cta button */
body.header--menu-open .header-menu-cta {
    display: none;
}

Hi,

What is problem on iOS?