This issue is commonly seen by users who run their own servers or VMs.  The easiest fix is to place an entry in your hosts file (linux: etc/host) pointing your domain to the local IP address. eg:

10.0.0.168  yourdomain.com

The reason the error occurs is because the webserver is converting a URL call to a local filesystem call.  This suggestion mitigates that issue.

Another way to mitigate the issue if you don’t have control over your server hosts file is to proxy your traffic through a free cloudflare account.  However, this requires changes to your DNS.

As of version 4.0.5 of Awesome Support we have created a possible work-around that might work for you.  Go to the TICKETS->SETTINGS->ADVANCED tab and scroll down to the Attachment Overrides section.  Turn on the Do Not Mask Attachment Links option.  Don’t forget to click the save button at the bottom of the page.