This is related to: Cannot load static content
Now that your CSS are hosted on a server asking for HTTPS, the company where I work filters it (HTTPS is authorized by whitelist only). I think a lot of companies do the same... Could you please put back the statics on a HTTP server?
To be more precise, this is the link that causes our issue:
<link rel="stylesheet" type="text/css" href="https://cdn.sstatic.net/stackoverflow/all.css?v=8a7874f4f2dd">