Which Sonos sound bar do you own? Try unplugging it from power for a couple of minutes and reboot your router and phone.

If there’s nothing showing at all from the device, when you power it on and you have tried different cables and wall power outlets, factory reset etc; then it sounds like a hardware fault. You could try getting it repaired locally perhaps, or trading it up for discount on another Sonos product, but first I would perhaps speak with Sonos Customer Care Staff, to perhaps see if they can assist and suggest anything further to try. You can contact/chat to them via this LINK