What would cause my smartphone to set off the Signal Loss Alarm with the Libre app?
Signal loss could be caused by the sensor being too far away from your smartphone.
For FreeStyle Libre 2 sensors: over 6 meters (20 ft)
For FreeStyle Libre 3 sensors: 10 meters (33 ft)
Additionally, the Signal Loss Alarm* can occur if Bluetooth is turned off, or another issue such as an error or problem with your Sensor.