FortiManager serial number change

Hi

I have a problem when my FortiManager rebuild and restore configuration, Fortigate device connection is down.

I follow below KB, but it seems not working.

https://community.fortinet.com/t5/FortiGate/Technical-Tip-How-to-replace-the-serial-number-of-a-FortiManager/ta-p/195106

Kyle_FMG-VM64 # diagnose fgfm session-list
FortiGate-60E(261) sn(FGT60Exxxxxxxxx) ip(10.10.10.67)
state(get auth) tunnel() uptime:unknown
Session count = 1 (tunnel 0, auth 1)

Thanks.