502 Error

Hi
I have a client who has your plugin for their CDN , they also have your assets pull addon. they always use the media to upload CDN with amazon, so they asked me to setup their assets pull for them. I followed your instructions word by word, but no matter what I get a 502 status error. even when I tried the amazon CloudFront subdomain direct link on the browser, I get the same error. I contact the hosting company and they checked and told me that they don’t have any blocking.
What is the issue here!?
is there any solution for this because this is really not making any sense, the site also has a wildcard SSL certificate installed by 3rd party, not a free Cpanel self-signing.