How Can I Fix a Gardtec 360/580 Alarm System?

I have recently moved into a new house which has an alarm fitted. The previous owner left me a manual for a Gardtec 360/580 and the master code. However the system was not working as he said it needed a new battery for the control box. I bought a new battery and fitted it and the system kicked into life but now constantly displays "Cb" which the manual says is Control Box Tamper. The master code doesn't clear this. Is there a way of clearing this error? Also, the LED does not flash on the outside box. Is there another battery in there that needs to be replaced?

Thanks for any advice.