Active underline of navigation links on hover

Site URL: https://www.thirstforallah.com

Hey all,

I recently purchased a plugin from squarestud.io and have been having trouble getting support regarding a plugin that causes my navigation links in the header to be underlined upon hover. See Nav Header One - CLICK HERE. This is currently only working on safari and does not work in chrome on my mac, but does work on my mobile in chrome. Any particular insight into what could be changed in the coding that could solve this problem? 

//Navigation underscore - squarestud.io//

nav a:hover {
    background-size: 100% 0.5px !important;
}
nav a {
  padding-bottom: 6px;
  overflow: visible !important;
background-repeat: no-repeat !important;
    background-image: linear-gradient(to right,currentColor 100%,currentColor 0) !important;
    background-size: 0% 0.5px !important;
    background-position: 0% 100% !important;
    white-space: initial;
transition: all ease-in-out 500ms !important;
-ms-transition: all ease-in-out 500ms !important;
-moz-transition: all ease-in-out 500ms !important;
-webkit-transition: all ease-in-out 500ms !important;
}
//End navigation underscore//

Additionally, if you are feeling particularly generous, on mobile the underline surpasses the boundary of the link and goes across the whole screen. See below. Really grateful for the help i've received thus far on this forum. Thanks for your help!