To fix a red LOS light on your router/ONT, start by checking that the fiber patch cord is firmly clicked into the ONT's PON port and undamaged, then power cycle the device for 30 seconds. When it's green and steady, everything is fine. If the light stays red, check your ISP's app or helpline for an area outage before calling support. Before you panic or call tech support, there are several simple fixes you can try at home that often solve this problem in minutes. Home routers use colored LEDs to convey different. The lights on your router serve as crucial indicators of its operational status. Internet Light: Indicates whether the router has an active internet connection.