Troubleshooting: "Unable to Load FortiGuard DDNS Server List" on FortiGate
Check Management VDOM: If VDOMs are enabled, ensure the management VDOM (usually 'root') has a valid route to the internet, as FortiGuard communication typically originates from there.
Test Resolution: Run execute ping service.fortiguard.net or execute ping www.fortinet.com from the CLI.
For persistent cases, engage Fortinet TAC with the diagnostic outputs from diagnose debug flow and execute curl to pinpoint the exact connectivity break.
Known Bugs: Version 7.0.0 had documented issues with DDNS loading that were largely resolved in later patches like 7.0.1.