Missing menu icon

Hi,

I have re-installed the template as advised on a test site but the icons are still displaying the original "F078" characters. Comments appreciated.

Hello,

In the custom.css file, you have this:

Please change it to this:

Regards,
Milos

Thanks again for all the help you are offering - it is appreciated.
I changed the custom.css file as advised but unfortunately still no change to the icons.

Hello,

Please change this line:

to this

Regards,
Milos

Thanks again. When changed as advised the icons remain the same "F078". However, something is fundamentally wrong. When I use Firefox inspector the code remains unchanged - see below:
.container_topmenu .parent > a::after {
background: none;
content: '\f078';
font-family: 'Font Awesome 5 Free';
top: 20%;
}
.container_topmenu .parent > a::after {

Just another snippet of info. When I use Firefox inspector to change the code as below, I get the required + icon. Obviously the custom.css changes are not working for some reason - different problem?!
code remains unchanged - see below:

.container_topmenu .parent > a::after {
background: none;
content: '\2b';
font-family: 'Arial';
top: 20%;
}
.container_topmenu .parent > a::after