I reached out to the support team before to have the sensor replaced the first time. I believe there is a flaw in the software of the base station. It appears to not be sending/ receiving supervisory signals to and from the sensors. I can open the cover on the sensor and the blue light comes on as well as when you open and close the door. I also noticed that if a sensor is left in the open state for an extended period of time it will also “go offline”. The only fix they had was delete and reinstall the sensor/ replace it. The manual rebooting of the sensor has no effect. I tried to explain this last time it occurred. It will keep happening until they figure out why it does that. Other wireless alarm systems will not go off line until the battery dies, no matter how long its left in the open state.