Trying to hide Nav bar from a single page

I’m trying to disable the bar at the top of this page so the slider I’m using goes all the way to the top of the screen. I’ve tried all the different CSS options I can find, but none have worked. These include:

.page-id-143 #nav-menu{
  display:none !important;
}

.page-id-143 nav#no-header-top-menu {
    display: none;
}

I’m really confused as to why nothing is working. I’m only trying to disable it on this one page as a test, and then I’ll do the same on my home page.

Thank you!

The page I need help with: [log in to see the link]