New Smoke Detectors continually alarm when connected
I would recommend you use a step by step approach to connect these up. 

I noticed you said each one the alarm sounds immediately. That sounded like you connected up the bases and then began stabbing in the detectors with the power on. I can tell you that electronic devices do not like that. So everything you need to do you should always do with the power off and then turn it on.

First turn the power off, then disconnect every base except for the first one, plug in the device and see if a single one works alone.

Then turn the power off and connect the next base, plug the device, turn the power on and see if they will work in tandem. If the device alarms then turn the power off and try using a different device, turn the power back on.

Keep repeating this procedure until you begin to isolated the problem. either a base is miswired or a device is defective. Or as the last resort a P12040 and a i4618ac are not compatible. That's why you need to contact the manufacturer. 

Hopes this helps.