Accenta8 - No power?

Accenta8 model. After a power cut the alarm went off, I managed to switch the alarm off but now there is no power to the RKP. I have replaced the battery, as it seemed a little low, but nothing has happened. There is a red light on inside the indoor box near to the RKP. There is just a red light on the outdoor alarm box, usually there is a red and green light flashing.
Grateful for any ideas