Font Awesome icons are not shown in production

After preparing and testing in local (and working perfectly), we have upload to pre-production (copying directories and database). Everything seem to work the same as in local except the Font Awesome icons (are shown as squares with numbers inside). We've checked every library, css, php without success. Even we have tried to change the relative call (fron theme.css in @font-face src: url) to a static one, or to include manually the theme.css file as link rel in theme.php... Nothing seems to solve such odd behaviour and we don't know what else can we check. Any hints? Thank you in advance.

Hi there,
sorry I dont know.
Maybe a mistake in server config which is not allweed to load these files.
Please check the https directive and the htaccess