For customers with fiber service, a battery backup similar to the one pictured below should have been installed for your service. It is normally in the garage or basement near to where the service comes in, or outside typically also near to where the service comes in. When the battery backup is working correctly, there will be two green lights on “AC” and “Output”.
If there are no lights on the battery backup, it means it is not getting power. Check to make sure the outlet the battery backup is plugged into has power, and check for tripped breakers, including GFI outlets that may need to be reset. The Battery backup may not necessarily be plugged directly into the GFI outlet, but could be plugged into an outlet that is protected by a GFI outlet elsewhere. GFI outlets should look similar to the picture below. Most times if the GFI is tripped the reset button on the outlet will be popped out.