some quick notes post fix:

On Fortigate run:

execute switch-controller get-conn-status <FortiSwitch_serial_number>

execute switch-controller diagnose-connection <Fortiswitch_serial_number>

on Fortiswitch run:

config system global

set switch-mgmt-mode fortilink

end

plugin console cable with known port open in Putty.

Eject the CF and copy firmware and rommon to it, or get it on the device via USB or TFTP etc.

Power on and “Ctrl+( right click putty > special command > break ) ” – repeat until

rommon 1 > confreg 0x2142


You must reset or power cycle for new config to take effect
rommon 2 > reset

upgrade rom-monitor file flash0:\"file name"

after rommon upgraded del flash0:/”all firmware but the newest bin” and reload

config t

config-register 0x2102

end

erase nvram:

copy run start