Unable to Download / Cache files of BES Relay & Client Upgrade files on Bigfix Server

Hello Team
I am trying to run a fixlet which is used to upgrade Bigfix Client and Relay to 9.5.11 on a Relay server in my environment which is running on 9.5.3 .
While running the fixlet to upgrade the client and relay, I get below error. Need your inputs to solve the issue,
My environment is running proxy and the proxy test is success .
Error : Download Error : “Unexpected HTTP response: 403 Forbidden”

I have added Bigfix Server , local host and loop back ip in the proxy exceptions , but still no luck.

Is your proxy allowing access to software.bigfix.com specifically?

@JasonWalker in downloadwhitelist.txt it is added. and in IE trusted sites as well.

It has to be some piece of network gear (proxy, firewall, etc.) giving the 403 error. Keep looking, try downloading it with a browser, try downloading with a browser from the server, check that Bigfix and your browser are using the same proxy settings.