since it doesn't work from outside your network, it's pretty much given that this is going to be a routing and/or firewall issue. Perhaps a DNS issue but we don't have enough detail to help you.
What is xx.xx.xx.xx in your case, an IP address, a fully quailified domain name?
Since you use the https prefix, it pretty much has to be a domain name.
Port 443 has to be open on your firewall and your router has to be configured to forward traffic on that port to the internal IP address or internal DNS name of your FMS box.
Thank you for your answer.
I reviewed the AWS security group setting and set the source to HTTP and HTTPS to "anywhere," then it works now.