Arrived On site FACP (Fire alarm control panel) Reflected NAC 2 Trouble Checked booster panel, found booster panel with out its AC Power Light On and Circuit board buzzing. Recycled AC and battery power. Panel still reflects same. Booster Panel is not recognizing its AC or Battery. However the NAC 2 Trouble appears to have gone away. Tested Fire Alarm system, system functions properly when Fire alarm is activated. Load tested (Customer Supplied Batteries) Batteries passed showing 12.6 volts and 11 amp hours each. Fire Panel is clear and normal at this time. However the Booster panel does require replacement. Informed staff that NAC 2 Trouble may come back over weekend until Booster Panel is replaced.