It is easy to Reset the Fortigate administrator password when you have physical access to the device, or if you can manage somehow to reboot the appliance from remote place, IYKWIM 😉 Here’s how.
Connect to Fortigate Console.
Reboot Fortigate, and login within 30 seconds after the login screen appears.
password: bcpbXXX, while XXX is the appliance serial number
reset the password:
config system admin
set password yournewpassword
Now you can login with username admin and use your new password.
See, it’s easy right? 🙂