Halcyon theme, icons not showing in services circles

Looking at Halcyon theme skeleton
https://demo.getgrav.org/halcyon-skeleton/
No icons are showing

I can confirm the same issue exists when skeleton is downloaded and installed locally. Does a plugin need to be installed for this to work? I checked the README.md but could not see any comment on this.

Thanks everyone x

Hello, it's because font-awesome is loaded with the http protocol instead of https.

You should search for this line:
<link rel="stylesheet" href="http://maxcdn.bootstrapcdn.com/font-awesome/4.7.0/css/font-awesome.min.css">

And change it to:
<link rel="stylesheet" href="//maxcdn.bootstrapcdn.com/font-awesome/4.7.0/css/font-awesome.min.css">

But it would be nice to create an issue on the Github repository so the creator can fix the issue.

Thanks that works perfectly. I have raised the issue on Github.