This is where junior admins cry. FortiGate firmware is not a ladder; it’s a game of Chutes and Ladders. You cannot jump from v6.0.15 to v7.2.9. You will brick the config. The firewall will boot loop, and you will be explaining to the CEO why the internet is down while you console into a flashing amber light.
Because when a zero-day hits at 5 PM on a Friday, you don't want to be fighting the Fortinet Support Portal login page. You want to be sipping coffee while SCP-ing the file to flash. fortigate firmware download
Put the mouse down.
So, you type the holy URL into your browser: support.fortinet.com . This is where junior admins cry