Fibre troubleshooting: lights, cables and no signal

The lights on your ONT tell you almost everything about the health of a fibre connection. Learning to read them means you can often diagnose a problem in seconds — and, just as usefully, know when it’s something you cannot fix yourself.

This guide follows the same order our technicians use.

Start with the status page

Before touching anything, check our network status page. If there’s a known incident affecting your area, we already know about it and are working on it — restarting your equipment won’t help and you’ll only lose time.

Reading your ONT lights

Light	Healthy	Meaning if wrong
Power / PWR	Solid green	No light: no power reaching the unit. Check the adapter, the plug and try another socket.
PON / Optical	Solid green	Off or slowly flashing: the ONT can’t register with our network. Usually a line fault or an account issue.
LOS	Completely off	Red or flashing red: Loss of Signal. The fibre is broken, disconnected or dirty. This one needs a technician.
LAN / Ethernet	Green, flickering	Off: the cable to your router is loose, unplugged or faulty.
Internet / Auth	Solid or flickering green	Off with a good PON light: possible authentication or account problem. Contact us.

Red LOS light

A red LOS light means the optical signal has been lost. There is nothing you can do about this from inside the house. Don’t unplug or attempt to clean the fibre — the connector is easily ruined. Report the fault with a photo of the lights.

The checks worth doing yourself

Photograph the lights. Before changing anything, take a clear photo of the ONT and router. Attaching this to a fault report often lets us diagnose without a site visit.
Check power to everything. Confirm both the ONT and the router are powered. Try a different wall socket — failed adapters and dead sockets are more common than people expect.
Restart in the correct order. Unplug both units. Wait 30 seconds. Power the ONT first and wait two full minutes for its lights to settle. Only then power the router. Doing both together is why many reboots appear not to work.
Reseat the network cable. The cable between the ONT and the router should click into both ends. Unplug and firmly reconnect it, or swap in a spare cable if you have one.
Confirm it’s in the right port. That cable must go into the router’s WAN or Internet port — usually a different colour from the LAN ports.
Test with a cable directly. Plug a laptop into the router with Ethernet. If that works but Wi-Fi doesn’t, the fault is in your wireless setup, not the fibre.
Look at the cable entry point. Check visually for obvious damage where the fibre enters the building — storm damage, a pulled cable, a strand caught in a gate. Report what you see; don’t attempt a repair.

Matching the symptom to the cause

What you’re seeing	Most likely cause	What to do
All lights off	No power	Check adapter, plug and socket. Try another socket.
Power on, LOS red	Fibre damaged or disconnected	Report the fault — a technician is required.
Power and PON good, no internet	Router, cable or account issue	Reseat the cable, restart the router, then contact us.
Works on cable, not on Wi-Fi	Wireless problem	See our Wi-Fi support page.
Drops repeatedly through the day	Marginal line, loose cable or overheating router	Report it with the times it happens — that pattern is diagnostic.
Slow but connected	Wi-Fi, device, or package capacity	See slow fibre speeds.

When to stop and call us

The LOS light is red or flashing red.
You can see physical damage to the cable outside or where it enters the building.
The ONT is completely dead with power confirmed at the socket.
The problem returns repeatedly after restarting.
You’re a business customer and are offline — phone us rather than using a form.

Make your fault report count

Include: the time the problem started, whether all devices are affected, a photo of the ONT and router lights, whether a cabled device works, and what you’ve already tried. A report with that detail is frequently resolved the same day.