simple custom css not displaying

hello,

i am using the vantage theme, currently the hover over the menu is blue i wanted to change it to another color, i used the following and updated css successfully and nothing changed on the website. where am i going wrong?

/* Menu */

.main-navigation a {
color: #e2e2e2 !important;
}

.main-navigation ul li:hover > a {
background: #00bcff !important;
color: #003300 !important;
}

https://wordpress.org/plugins/simple-custom-css/