Font awesome + Developer Kit problem

I have add Developer Kit (Apache Handlers) to my test site and it works fine with LESS modification. But I see no Font awesome symbols on pages. As I comment Compiler and Compressor all shown again.

Should I make something to overrun this problem? 

What does the F12 web console say? Are there any errors or failed requests.

I have seen hosts where the content headers for text/css were removed and replaced with text/html. That will make css fail in Chrome.

No errors. 
And I've never seen a more correct page before. Always there are some error and warnings but not in LiteCart.
Could it be due a my local server with a firewall restriction?

Ok. I just found it.
As You proposed, I took a close look on /ext/fontawesome/css/font-awesome.min.css loaded in page.
And found this

 Warning: strtotime(): It is not safe to rely on the system's timezone settings. You are *required*
to use the date.timezone setting or the date_default_timezone_set() function. In case you used any of those
methods and you are still getting this warning, you most likely misspelled the timezone identifier. We selected
the timezone 'UTC' for now, but please set date.timezone to select your timezone.
in D:\Internet\www\root\LC\handlers\less-scss-compiler.php on line 156 /*! * Font Awesome 4.7.0 by @davegandy - http://fontawesome.io - @fontawesome * License - http://fontawesome.io/license (Font: SIL OFL 1.1, CSS: MIT License) */@font-face{font-family:'FontAwesome';src:url('../fonts/fontawesome-webfont.eot?
....

So I delete line 156 in less-scss-compiler.php

header('Expires: ' . gmdate('r', strtotime('+7 days')));

Problem has gone.

Thx for Your attention.