So, I had the same brinks system, and chose to buy the same DSC kit, which went in nicely (took me a bit to get the hang of a few things, but overall not bad)
I had to install a new siren because the Brinks one was missing (fun time finding where the wire for it went!)
Everything is working nicely now except the glass-break. If I clap my hands or bang pots by it, or throw keys against a nearby window (not too hard now!), I see the green LED on the sensor mounted on the ceiling blink, but it doesn't seem to trip the system. I had the system armed in away mode, and the zone is configured as 'interior'
Is there a configuration step I've missed? I powered the sensor off Aux, and connected the other two wires to a zone.
How do I troubleshoot this further?