Troubleshooting Tip: Unable to upgrade FortiGate Firmware, the upgrade option is grayed out

The Upgrade button under FortiGate -> System -> Firmware is grayed out in some cases, even when a new version of the firmware is available, preventing the upgrade process from proceeding. See the screenshot below:

This issue occurs when the firmware upgrade is triggered via Fabric Upgrade instead of the standard Upgrade option in the FortiGate GUI.

Note that:

• If the FortiGate is not part of a Security Fabric or is operating as a standalone unit, it will not initiate a firmware installation through Fabric Upgrade.
• In such cases, the upgrade option will remain grayed out until the Fabric Upgrade process is canceled.
• Using the following command Fabric Upgrade process can be canceled using the CLI:

execute federated-upgrade cancel

Once the Fabric Upgrade is canceled, the Upgrade option will become available, allowing the firmware upgrade to proceed as expected.
Note: Make sure that the admin user has a read write access to the FortiGate. Otherwise, the user will see the upgrade option greyed out.

Related article:

Technical Tip: How to Cancel FortiGate upgrade using Fabric Management Page (Fabric Upgrade)