Power supply issue
The fiber modem is a small device set up between the fiber outlet and your Internet Box/b-box. Several models are available (see image above). It is connected to the red WAN port on the Internet Box/b-box by an Ethernet cable. It must also be plugged into a power socket.
Check that it is plugged into a power socket and that there is no power outage..
Are you currently experiencing a power outage (in the building, in the neighborhood, etc.)?
No, there's no power outage
Yes, there's a power outage