Sticky header question

Hi all,

When I try to use this sticky header snippet here, it causes the posts and sidebars to shift upwards to the very top of the page, which puts the sidebar widgets and posts behind the header, all weird the site is currently in maintenance mode, when I remove the sticky header snippet everything is good.

can someone tell me what is going on, I would be very grateful for any help.

/* Make Header ‘Sticky’ */
.tc-header {
position: absolute;
top: 10px;
background-color: #000;
z-index: 1000;
width: 100%;
height: 62px;
box-shadow: 0 4px 2px -2px gray;
margin-bottom:10px;
}