Troubleshooting Tip: After upgrading the firmware device does not come up. Only power LED is up

• When connected to the console, the error 'unable to load OS, CPU profile stopping' appears.

• The above issue happens, when the wrong upgrade path is followed, need to follow the upgrade path while upgrading the firmware.
• After connecting to the console, need to interrupt the boot menu by pressing any key and pressing key 'B' to load the backup firmware.
• The device will be rebooted with the backup firmware, and the device will come up with the old firmware and follow the upgrade path to upgrade the firmware.
• Follow the below link to check the upgrade path: Upgrade Path Tool Table
• To upgrade firmware, follow the below link: Technical Tip: How to upgrade FortiGate firmware

Note:

In this scenario, it is not necessary to reset or format the firewall as the issue occurred due to the wrong upgrade path. Loading the backup firmware by interrupting the boot menu by pressing 'B' is sufficient