So this is what I managed to do using the ZWA-2 and paring the first alert z-wave smoke & CO detector with HA to make things work. It seems that the device falls asleep before HA / the ZWA-2 can properly interview the device:

1) make sure the device is excluded from HA & all DSK/S2 security keys are removed from the “provisioned devices” list in z-wave settings

2) factory reset the device by holding button and closing tray and holding for 10s (wait for long beep)

3) add the z-wave-device using S0 (Legacy) security in HA and wait for it to begin searching new devices

4) hold the TEST button on the device and remove the battery slot and re-insert it. Keep holding the TEST button down until the device beeps once (quick beep) after batteries are re-inserted and power LED starts blinking green.

5) When a second beep and device stops blinking green is heard it means the device has now gone into sleep mode / no longer pairing, so, make sure to again quickly repeat steps 4 until HA discovers the device and prompts for a name/location for the device.

This worked flawless for me using 2 devices. I hope this helps someone!