Gardtec 300 display not registering but lit?

I've recently moved into a new house and carried out alot of work. During which the power has been on and off and walls demolished. Consequently the display unit for my alarm is lit but not showing anything on the LCD display. There is continuity on the data in & out wires from the control unit to the user control.

Is it likely to be a flat battery or a fault with the components? any help would be appreciated.

Thanks.