Troubleshooting Tip: Fabric upgrade stuck at 'Upgrade will start shortly' on FortiGate

When initiating a Fabric upgrade on a FortiGate, the device shows the message 'Upgrade will start shortly'.

However, even after waiting for an extended period, the upgrade does not proceed. No changes are applied to the firewall, and the message persists.

• Check the Fabric federated upgrade by using the following command:
  
  execute federated-upgrade status
  Global devices:
  1 FortiGate
  Local devices:
  Includes this FortiGate: yes
  Local status: downloading
  
•  
• Cancel the Fabric Upgrade:
  • Use the CLI command to cancel the ongoing upgrade:
    

execute federated-upgrade cancel
This will cancel the upgrade. If the upgrade is immediate or scheduled to happen very soon,
some nodes may have already gone down for upgrade.
Do you want to continue? (y/n)y

• This will stop the current upgrade process and clear any stuck tasks.

• Verify FortiGuard Connectivity:
• Check that FortiGate has connectivity to FortiGuard servers. Check the settings:
  

config system fortiguard
    set fortiguard-anycast disable
    set protocol udp
    set port 8888
    set sdns-server-ip 208.91.112.220 173.243.140.53 210.7.96.53
end

• Confirm that DNS resolution and Internet connectivity are working.
• Make sure no firewall policies or network restrictions block outgoing traffic to FortiGuard servers.

• Clear the browser cache:
  • Clear the browser cache and cookies, or try accessing the GUI using a different browser or incognito mode.
  • Alternatively, try accessing the FortiGate GUI in incognito/private mode or using a different browser.

• Check for Configuration Errors:
  • Identify any configuration issues that may block the upgrade.
  • Resolve any errors found before retrying the upgrade.

diagnose debug config-error-log read

• Retry the upgrade:
  • After canceling the previous upgrade and verifying connectivity and configuration, attempt the upgrade again.
  • Use the standard 'Upgrade' option instead of the Fabric Upgrade option if the issue persists. 
    Utilize the 'File Upload' method, or let the device download the images directly via FortiGuard. Refer to the article below for guidance: Technical Tip: How to upgrade FortiGate firmware.