Some Android users are puzzled about the behavior of the firmware update and why the Sensor always disconnects during this process. This behavior is completely normal, and was implemented intentionally in this way, to be able to transfer a big new Bluetooth update to your Sensors.
This firmware update process needs to be done only once and only for users who have never updated the sensor firmware.
This is what you have to do:
Connect the Sensor with your Android Smartphone. The App detects that you have an old Firmware. The Sensor disconnects to prepare the Firmware update. Then you press the sensor button for 10 seconds to reset the sensor. Then you click next, pair again and the update begins. Once the update is complete, the sensor led blinks red and the sensor disconnects again (yes, this is normal and needs to happen!). Now the update was successful and you can get started. The latest Sensor Firmware Version is 1.95