Keith,
Wireless devices are supervised by system, this is achieved by the devices sending a “check in” signal every 60 mins. The system must see a Security related device checked in at least once in 24 hours to prevent a missing trouble condition. Fire and CO devices must check in once every four hours.
The missing trouble condition is triggered when the system does not see the CO device send a signal for in four hours.
If this is not range related it could be a sensor going bad. We’re happy to work with you get it swapped out.
Thanks,
Mike