Custom mobile breakpoint with CSS for Fulton template

The Fulton template doesn't feature a customizable breakpoint in Site Styles but I want to adjust the default mobile breakpoint for the template. I've tried some custom CSS but I seem to be missing something (see below). It's not throwing any errors but it's not switching to the mobile menu at 1300px. 

Help, please.

@media only screen and (max-width: 1300px) {
#mobileNavToggle
  {
    display: inline-block;
  }
}