Hm, is pretty weird. It seems that the server is cancelling the request of some files in the admin panel, when you don't see any style is because of this:
But that doesn't happen always, sometimes it loads this css file but it fails on the js files and in the subsecuential files, ie:
This happens because your server is blocking/cancelling this request. When you fetch this URL directly in your browser address bar it loads OK, so the problem is that your server is somehow cancelling this subsecuential request.
The solution for this (script side) is that Chevereto should not load this static files using PHP, I've already done this on your server by changing this on the root .htaccess file:
Code:
RewriteRule ^admin/(.*) admin/index.php [L]
To this:
Code:
RewriteCond %{REQUEST_FILENAME} !-f
RewriteCond %{REQUEST_FILENAME} !-d
RewriteRule ^admin/(.*) admin/index.php [L]
That is a quickfix to load static admin files without PHP (this fix will be addressed on 2.3 on a more simple way). But in your case it doesn't solve anything because once you login in the admin panel you will notice that is not working 100% because your server is shouting down some json calls, like the query to get the total uploaded files. You can check this on the browser console.
I'm afraid that your server is not properly setted, This is the first time that I notice this weird error. You should contact your hosting company about this.