If the unset light is flashing it means it's just being supported by the backup battery so there's no mains supply, this could be due to the fuse in the fused spur has blown (if one has been installed) or the quick blow fuse in the main control panel, or the circuit which it's connected to or if it's on its own circuit which is from the main DB (distribution board) has tripped.
Paul m, November 2017
