Brand new contact sensor shows 'battery out of power', but it works only in disarmed mode

I’m just installing my first contacts sensor (gen 2). Every time I open the door, I hear a chirp and see a brief green light. I also see in the device history that the door was opened or closed.
Everything seems to work as I expect until I try to change to home or away mode. Then the keypad says ‘sensors require bypass’. I also see ‘battery out of power’ for that sensor in my app. I can’t believe that the batteries would be low when I just removed the plastic tab, and I can’t believe the sensor would work so well if the batteries are out of power. Is there something else that could be causing this?

Hi @user39768. It’s unlikely that the battery would be low upon the initial setup. I’d recommend trying the troubleshooting steps listed here for your Contact Sensor. If it’s still reporting a low battery after that, try inserting a new battery to test it out. If the message goes away, then there was an issue with the original battery. If the message does not go away, it would be best to follow up with our support team to investigate what’s wrong with the Contact Sensor itself.