Troubleshooting Tip: Error happened when verifying FDN Server (globalupdate.fortinet.net:443) certificate: FDN ca certificate changed

Description

This article describes how to restore the connection during error occurs when verifying the FDN Server (globalupdate.fortinet.net:443) certificate: FDN ca certificate changed.

Scope

FortiSandbox.

Solution

Unable to update a certain/specific module with error showing 'FDN Connection or Download Failure'.

Navigate under the Logs & Report -> Events -> System Events, logprint 'Error happened when verifying FDN Server (globalupdate.fortinet.net:443) certificate: FDN ca certificate changed.' can be seen.

Solution:

Perform diagnose-debug fdn to debug to issue:

End of keyboard-interactive prompts from server
[?2004hFSA3000E-SANDBOX> diagnose-debug fdn
[?2004l
2026-04-27 12:56:08.345:: Debug: start FDN process 3487.
2026-04-27 12:56:08.345:: Debug: run fdndownload
		------------    START: FDN update for firmware v5.06,build0155 (GA)    ------------
2026-04-27 12:56:08.348: DEBUG: AntiVirus Scanner version: 00007.00049
2026-04-27 12:56:08.348: DEBUG: AntiVirus Signature Patch version: 00000.00000
2026-04-27 12:56:08.348: DEBUG: AntiVirus Active Signature version: 00093.17017
2026-04-27 12:56:08.348: DEBUG: AntiVirus Extended Signature version: 00093.17008
2026-04-27 12:56:08.349: DEBUG: AntiVirus Extreme Signature version: 00093.17010
2026-04-27 12:56:08.349: DEBUG: Network Alerts Signature version: 00002.04929
2026-04-27 12:56:08.349: DEBUG: Industrial Security Signature version: 00036.00208
2026-04-27 12:56:08.349: DEBUG: Sandbox Contract version: 00000.00000
2026-04-27 12:56:08.349: DEBUG: Traffic Sniffer version: 00007.00183
2026-04-27 12:56:08.349: DEBUG: Sandbox Tracer Engine version: 05000.00051
2026-04-27 12:56:08.349: DEBUG: Sandbox Rating Engine version: 05000.00056
2026-04-27 12:56:08.350: DEBUG: Sandbox AI Engine and Model version: 05000.00035
2026-04-27 12:56:08.350: DEBUG: Sandbox System Tools version: 05000.00080
2026-04-27 12:56:08.350: DEBUG: AntiVirus Active Signature Delta version: 00000.00000
2026-04-27 12:56:08.350: DEBUG: AntiVirus Extended Signature Delta version: 00000.00000
2026-04-27 12:56:08.350: DEBUG: AntiVirus Extreme Signature Delta version: 00000.00000
		------------    START: fetch new FDN server list.    ------------
2026-04-27 12:56:08.350: DEBUG: Start querying fds1.fortinet.com to get available FDN server list
2026-04-27 12:56:08.351: DEBUG: send cmd /usr/bin/updclt -c AES128-SHA:DES-CBC3-SHA:AES256-SHA DestHost=fds1.fortinet.com DestPort=8890 'Protocol=3.1|Command=Setup|Firmware=FSA3KE-5.0-6-0155|SerialNumber=FSA3KET319000108|Persistent=false' -T 30 -d /drive0/private/updtool/
<TRUNCATED>
2026-04-27 13:16:54.933: Error: cannot find FCPR code for Sandbox Rating Engine from fds1.fortinet.com:8890
2026-04-27 13:16:57.937: Error: failed to update Sandbox Rating Engine
		------------    END: update Sandbox Rating Engine    ------------
2026-04-27 13:16:57.938: INFO: Set next update time for sysrater: 1777274177 (in 3560s)
		------------    START: update Sandbox AI Engine and Model    ------------
2026-04-27 13:16:57.938: Sandbox AI Engine and Model contract expired, skip update AI Engine and Model.
2026-04-27 13:16:57.938:: Debug: AI engine version: 05000.00035.

If the FCPR error shows it is unable to resolve fds1.fortinet.com:8890, try to change the setting under System -> FortiGuard -> FDN Server Location: Nearest to help resolve the issue.