Header not positioning correctly in IE - html

Question

Working on a header and currently using Flexbox to position the header and everything is positioned center correctly like I want when I test locally on my Mac but when others on my team are testing in IE or Windows based machines the header is no longer being positioned in the center. It becomes full width positioned either left or right and I'm really not sure what I am missing or doing incorrectly. Any help would be appreciated.
What it should look like
What it's doing on a Windows machine
html
<header class="mcc-header ember-view">
<div class="mcc-full mcc-div">
<div class="mcc-header-content">
<a href="/" class="mcc-header-logo">
<span class="mcc-logo-title">MCC Semi</span>
</a>
<ul class="mcc-header-nav">
<li class="mcc-header-nav-item">
Company Profile
</li>
<li class="mcc-header-nav-item">
News
</li>
<li class="mcc-header-nav-item">
Contact Us
</li>
<li class="mcc-header-nav-item">
EN | CN
</li>
<li class="mcc-header-nav-item">
</li>
<li class="mcc-header-nav-item">
Login
</li>
<li class="mcc-header-nav-item">
Sign Up
</li>
</ul>
</div>
</div>
<div class="mcc-full">
<div id="main-menu" class="mcc-header-menu">
<div class="mcc-full">
<div class="mcc-header-legal">
<ul class="mcc-header-legal-list">
<li class="mcc-header-legal-item">
Products
</li>
<li class="mcc-header-legal-item">
Catalog
</li>
<li class="mcc-header-legal-item">
Applications
</li>
<li class="mcc-header-legal-item">
Quality
</li>
<li class="mcc-header-legal-item">
Calendar
</li>
</ul>
</div>
</div>
<form class="mcchf" id="mcchf-h-search" action="" method="get" title="" role="search">
<label class="mcchf">Search</label>
<input class="mcchf" id="mcchf-h-st" type="text" name="q" placeholder="Search">
<label class="mcchf">Submit search query</label>
<input class="mcchf" id="mcchf-h-sb" type="submit" value="">
</form>
</div>
</div>
</div>
</header>
css
.mcc-header {
background-color: #fff;
display: block;
padding-bottom: 24px;
position: fixed;
width: 100%;
height: 90px;
top: 0;
left: 0;
padding-right: 50px;
padding-left: 50px;
z-index: 800
}
.mcc-header-content {
display: flex;
flex-direction: column;
padding-top: 6px
}
.mcc-header-nav {
column-count: 2;
display: block;
width: 100%
}
#media screen and (min-width:760px) {
.mcc-header-content {
flex-direction: row;
justify-content: space-between;
padding-bottom: 0
}
.mcc-header-nav {
column-count: 3;
width: auto
}
}
#media screen and (min-width:1020px) {
.mcc-header .mcc-header-content {
align-items: flex-start;
padding-top: 0
}
.mcc-header .mcc-header-nav {
column-count: 1;
width: auto
}
}
.mcc-header-nav-item {
display: block;
text-align: center;
width: 100%
}
#media screen and (min-width:1020px) {
.mcc-header .mcc-header-nav-item {
display: inline;
text-align: left;
width: auto
}
}
.mcc-header-nav-link {
display: block;
margin-bottom: 0;
padding-bottom: 20px;
padding-top: 4px;
white-space: nowrap
}
#media screen and (min-width:760px) {
.mcc-header-nav-link {
display: inline-block;
padding-right: 24px
}
}
.mcc-header-legal {
border-bottom: none;
display: flex;
flex-direction: column;
justify-content: center
}
.mcc-header-legal-list {
display: block;
text-align: center;
}
#media screen and (min-width:760px) {
.mcc-header-legal {
align-items: baseline;
flex-direction: row;
margin-top: 0
}
.mcc-header-legal-list {
text-align: left
}
}
.mcc-header-legal-item {
display: inline-block;
padding-right: 24px;
padding-top: 24px;
text-align: left;
white-space: nowrap
}
.mcc-header-legal-item:last-of-type {
padding-right: 0
}
#media screen and (min-width:1020px) {
.mcc-header .mcc-header-legal-item {
margin-left: 0 !important;
padding-top: 8px
}
}
.mcc-header-logo {
display: block;
flex-shrink: 0;
padding-bottom: 0;
padding-top: 8px;
position: relative
}
.mcc-header-logo .mcc-logo-title {
height: 1px;
width: 1px;
position: absolute;
overflow: hidden;
top: -10px
}
#mcchf-h-search {
position: absolute;
top: 56px;
right: 5rem;
width: 250px;
height: 22px
}
#mcchf-h-search label.mcchf {
display: none
}
#mcchf-h-st {
position: absolute;
right: 30px;
width: 225px;
height: 22px;
padding-left: 5px;
cursor: text;
color: #111;
border-bottom: 1px solid #000;
border-top: none;
border-left: none;
border-right: none;
background: #fff;
-webkit-appearance: none;
border-radius: 0;
text-transform: none
}
#mcchf-h-sb {
position: absolute;
top: 0;
right: 0;
overflow: hidden;
width: 18px;
height: 18px;
cursor: pointer;
white-space: nowrap;
color: #000;
border: 0;
background: url('');
}
input {
display: block;
margin-bottom: .667em;
font-family: inherit;
font-size: 1rem;
line-height: 1.333em;
text-transform: uppercase;
-webkit-font-smoothing: antialiased;
-moz-osx-font-smoothing: grayscale;
background-repeat: repeat-x;
background-size: .09em .09em;
background-position: 0 90%
}