Add box-shadow to sticky navigation.

Hi, I want to add a box-shadow to my sticky-navigation.
My sticky-navigation is set to "Hide when scrolling down".

Currently, I am using this code:
#site-navigation {
box-shadow: 0 1px 8px 1px #ccc;
}
But, this code only shows the box-shadow when I am at the very top of the page.

It doesn't show the box-shadow while I am scrolling up.

How to get box-shadow while scrolling up?

Website link: https://www.clichemillennials.com/blog/

Thanks.