In rare occasions it could happen, that the computer of the system does not start up after a power outage or hard power off. In these cases the computer needs to be started again manually.
The computer is located in the big metal box underneath the ceiling. The computer is located at the back of the box. A latter is needed at least to reach it. If there is no blue led visible the computer is off.
The switch to turn it on is located at the left next to the LED:
