Attempt to log in using the original credentials for the default account. Access is denied.
Log in using the new credentials for the default account. Access is granted.
Go to Log & Report > System Events. You can see the successful and failed login attempts in the events list.
For system events to appear in the GUI, you must configure disk logging in the log settings on the FortiGate. This option is only available on FortiGate models that have an internal hard drive.