There's always a reason,
usually down to user error,or there's a system problem,
tell us more, so we can hopefully establish what's going on,
does this happen when the system is armed or unset or both ?,
does the keypad respond,eg can you silence the alarm immediately using your user code ?
what LEDs are lit on the panel and keypads ?,
Are any LED/s winking at you,and if so what colour?
so basically you are looking for the day,tamper,zone, LEDs that are lit, and any that are blinking.It could be a control backup battery issue,but its impossible to say on the info you have given.
e manno, May 2012