Can not enable FortiGuard DDNS from the GUI
Description
Sometimes, when you want to use the FortiGuard DDNS. But when you go to System >Network >DNS
and you may notice that the check box of the "FortiGuard DDNS" feature shows grey out as following.

Solution
Instead, run the following CLI commands to enable use of FortiGuard DDNS.
For example :
Sometimes, when you want to use the FortiGuard DDNS. But when you go to System >Network >DNS
and you may notice that the check box of the "FortiGuard DDNS" feature shows grey out as following.

Solution
Instead, run the following CLI commands to enable use of FortiGuard DDNS.
| FGT # config system ddns FGT # edit 1 FGT # set ddns-server FortiGuardDDNS FGT # set ddns-domain <name.fortiddns.com> FGT # set monitor-interface <interface> FGT # end |
For example :
| FGT # config system ddns FGT # edit 1 FGT # set ddns-server FortiGuardDDNS FGT # set ddns-domain "TAC24.fortiddns.com" FGT # set monitor-interface "wan1" FGT # end |