For LOS (Loss of Signal) red lights on fiber or advanced gateways, it usually means the incoming optical line is not detected or has low signal. Double-check that the fiber line is connected properly and that there's no bend or physical damage. If issues persist, an on-site. This guide will walk you through what the LOS light means, why it blinks red and step-by-step instructions on how to resolve the issue, including resetting your router. Sometimes it may be due to a problem with your internet service provider, although you could also be experiencing this issue due to improper configuration of your router, a poorly connected cable, etc. ”. Routers can overheat, which may lead to functionality problems. It can also indicate your router is undergoing a firmware update, temporarily losing its link to the internet or local network.