c & K securitech alarm. Mains and Daytime lights no longer light up on keyp?

I have a securitech 700L alarm system. The mains light and daylight recently went off and have not come back on although the alarm still works and sets. We had an alarm engineer check this out and the mains supply and battery all test okay. As he has no understanding of C & K alarms he was unable to help any further. Any ideas