The requested URL /build/20151017.205330.753468218/ was not found on this server.
During each build request the current model attempts to remove/purge any builds that are more than 24hrs. Your build request shows in the server logs as:
Oct 17 23:46:55 live-build-cgi live-build-cgi: end web build (20151017.205330.753468218: maybe-successful).
So all went well, it would appear that the automation system purged your build before you could download.
So just submit and attempt to access build within 24hrs of request.