My Optima XL6 intruder alarm the key pad is not responing?

I have a OPTIMA XL6 ALARM SYSTEM that has been working everyday for years with no problems.
My RED & GREEN light are on as normal but when I tried to set it last night the keypad buttons are not working I have pressed the reset button, but any number i press has no effect the keypad is dead,but red&green lights are on as normal.Has anyone any ideas please.