Sensors not detecting movement?

Our home alarm system has sensors in 3 zones, the panel lights up if theres movement in any of the zones, preventing arming the alarm. We came home one day to find the alarm with all 3 zones lit up and a constant beep. The code was entered to stop it. However the 3 zones still show as detecting movement.

Ive been able to establish the alarm still works, that switching the power off for 30seconds (with the battery disconnected) then switching it back didnt help and the wiring to the sensors is ok (discovered this by trying to take a cover off one of the sensors and setting the alarm off), however there does not appear to be any movement detection happening on any of the sensors. Any ideas?

The alarm is a Sentinel 1 by National Fire & Security company (tried to google them but couldnt find anything)

Jason
June 2006