This is a HTTPS request, see the referrer:

[1] request for www.#########.com/test/predator/webclient.swf?v=1.0.777:
<<< GET /test/predator/webclient.swf?v=1.0.777 HTTP/1.1
<<< Referer: <http://www.#########.com/test/predator/>
<<< Connection: close
<<< Host: www.#########.com
<<< User-Agent: Mozilla/5.0 (Windows NT 6.1; WOW64; rv:49.0) Gecko/20100101
Firefox/49.0
<<< Accept:
text/html,image/png,image/jpeg,image/pjpeg,image/x-xbitmap,image/svg+xml,image/gif;q=0.9,*/*;q=0.1
<<< Accept-Language: en,*
<<< Accept-Encoding: gzip, identity;q=0.9


Result: Error 403

Without referrer, or with https referrer, all works