My transparent header in mobile is missing

My site is: 3dux.co.uk

I’ve got a transparent header that hides on my site for when scrolling down using the following code as shown in a Wix tutorial using the following code:
export function header_viewportLeave(event) {
$w(‘#whiteHeader’).show();
//Add your code for this event here:
}
export function header_viewportEnter(event) {
$w(‘#whiteHeader’).hide();
//Add your code for this event here:
}
The problem is that the transparent header in mobile is hidden and whenever I try to show it, it hides again.
Please help.
Thanks,