Conbee II -> SMaBiT Siren

I am building my alarm system on the Alarmo plugin which is working fine. Then I am trying to add an outdoor siren, which is thr SMaBiT AC2010/29A Siren
https://manuals.smabit.eu/av2010_29a.html

I’ve added the Siren as “light” in Phoscon. It works fine. But when adding the siren as an action for when the alarm activates, but it only comes with a very descrite “bip”. It feels like it just turns on and off instantly.

Any thoughts on how to make this work?

Thanks
Jacob