Troubleshooting Tip: After upgrading FortiGate to version 7.6.6, FortiManager Cloud gets disconnected

User configures a FortiManager cloud connection in the FGT using the FQDN connection

config system fortiguard
    set auto-firmware-upgrade disable
end
config system central-management
    set type fortimanager
    set serial-number "xxxxx"
    set fmg "fortimanager.forticloud.com"
end

In the logs, validate that the connection status is unknown:

FG-test# diagnose fdsm central-mgmt-status
Connection status: Down
Registration status: Unknown
Serial:

In the debugs, verify the DNS is unable to resolve the FortiManager cloud domain:

2026-02-17 16:57:35 FGFMs: using /etc/cert/factory/root_Fortinet_Factory_Backup.cer and
/etc/cert/factory/root_Fortinet_Factory_Backup.key for client site authentication
2026-02-17 16:57:35 FGFMs: fgfm_fqdn_connect,183:Connect to fortimanager.forticloud.com.
2026-02-17 16:57:35 FGFMs: fgfm_dns_query: try to bind (fortimanager.forticloud.com)

In the DNS debugs, verify FortiGate is stuck trying to solve the domain *fortimanager.forticloud.com:

diagnose debug application dnsproxy -1

diagnose debug console timestamp enable

diagnose debug enable

Verify the DNS cache dump using the below command:

diagnose test application dnsproxy 7  <----- Look for the domain entry here.

And confirm the DNS configuration on the FortiGate:

config system dns

    set interface-select-method auto  <----- Make sure the selected interface is active if specified.

end

Validate the DNS proxy process is using around 80% of a core:

get system performance top

Solution.

Identify which is the process ID of the dnsproxy using the following command:

diagnose system process pidof dnsproxy

Kill the process with a signal 11:

diagnose system kill 11 PID

Special note:

Restarting the DNS proxy by the name of the process does not solve the issue.

fnsysctl killall dnsproxy