Help briked router

Hi guy i have a routed Digicom 8E4570 Modem Router Wireless N 300Mbps, ADSL2+, 4 Porte LAN 10/100
have this mother board 10016318 v1.0 and have a cpu bcm6318 broadcom
i try to install a firmware
891 Sagem F@ST2704N V1 17.01.4 DSL modem, WiFi 2.4 GHz partly Broadcom BCM6318 brcm63xx smp https://downloads.lede-project.org/releases/17.01.4/targets/brcm63xx/smp/lede-17.01.4-brcm63xx-smp-FAST2704N-squashfs-cfe.bin View/Edit data
and installation go , but after restart , not see the router and i think is bricked
i find a serial connector over the pcb and i solder 4 cable (probably one is not used), someone can help me or giveme a tutorial for reload a firmware???
thankz

See the LEDE User Guide section Failsafe Mode and Factory Reset...

https://lede-project.org/docs/user-guide/failsafe_and_factory_reset?s[]=failsafe

i tryed but nothing , i must use serial ???