The batteries are flat in the Wireless Room Sensor and the sensor will have stopped working altogether.
First, remove the front cover of the Wireless Room Sensor by placing a tool (such as a flat-bladed screwdriver) into the top of the sensor until you hear a click. This will release the catch.
Use your nails or the screwdriver to pull the white (front) of the room sensor away from the clear (back) and allow the cover to swing down (be careful not to pull the sensor off the wall).
The front is hinged at the bottom.
Remove the CR123 battery by pushing it lightly against the spring.
Wait 30 seconds before putting in the new battery.
Put in the new CR123 battery.
The light will flash once every second for 30 seconds.
Wake the device by pressing the black button at the top left of the device once.
Your system will take around a day to update with your devices values and for any errors to clear
*** Verification Test to ensure messages queued and then battery level is now > 50% ***