I fixed one recently an elite , similar system , has an external bell was installed by a builder not bad lol, freaked me out why it wouldn't set
The builder clever one put the garden door sensor into the frame on a bifold after years slamming the door damaged the reed , I thought that was it but theres a gap behind the magnet side and the magnet itself and popped out from behind into the frame so not allowing alarm to set and always showing active
Standard flush round magnet mounted on pillars into door , groove in door is where magnet was