Problem scenario
You installed CraftCMS. But there is no port activity on port 80. You want to go to the front-end now. You cannot get to it via a web browser. What do you do?
Solution
Is there a firewall or public cloud security group (e.g., an Azure Network Security Group) blocking traffic to the public IP address over port 80? GCP's firewall could block HTTP traffic such that nmap commands would not show activity over port 80. An nmap -Pn x.x.x.x command could return neither a port filtered/closed response if GCP's firewall was configured to govern the server to block HTTP traffic.