Remove Active Navigation Underline

Site URL: https://canberrastrata.squarespace.com/

I am trying to remove the underline from all links on this site. I have successfully done it for most but cannot seem to get the active navigation line removed. I have tried code that has worked on previous websites but it is not working on this one (7.1). 

https://canberrastrata.squarespace.com/ 

Password: strata

Hi,

Use this code

header#header a:after {
    opacity: 0;
}