If you can't use the on-board relays on the Vista 20P you may need another way to indicate armed/disarmed status.
I added a 4229 expander board to the system and used the one relay on it to indicate armed/disarmed status. Because the relay has no voltage, you need to supply it. I used the Konnected board to supply it +5V.
The diagram is below. Hope that helps other folks.
ALso if you are using multiple zones with 4-wire smoke detectors the pins on the Vista20P may be used! You'll need an expander to make it work!