Optima XM6 - No buttons work after power cut?

Hi,
My parents had a power cut which set off their alarm. Power is back now but for some reason if I press any of the buttons on the front panel, nothing happens. No tones, nothing at all. The power light is on. If I remove the fuse which goes to the panel, the external alarm sounds and when replaced it goes off but I can still not do anything on the panel itself.
If you have any ideas or a resolution, please give me a call on 07799 645859.

Thank you.