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 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???

See the LEDE User Guide section Failsafe Mode and Factory Reset...[]=failsafe

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