Theme Horse

Hi, I want to make a menu with colors that are displayed in a gradient way, but in the css customizer, the css code that I apply does not work.
this is the code i use.

.navbar-main {
-webkit-box-flex: 0;
-ms-flex: 0 0 100%;
flex: 0 0 100%;
max-width: 100%;
-webkit-box-ordinal-group: 2;
background: -webkit-radial-gradient(center center, circle, #a267a1, #5F267D );
-ms-flex-order: 1;
order: 1;
}
the web is radiotucuman.com