@danfelix, cool, glad to hear that news. I bet I know why the siren won’t trigger. It’s because (I think) certain commands are not there yet in ST default device type - Zwave Siren. You can try my device type if you want. It should help:
What it looks like when inactive:
Link to the code to copy/paste:
https://raw.githubusercontent.com/constjs/SmartThings-Devices/master/utilitech_siren_v2.device.groovy