Pairing the breathalyzer requires your smartphones' Bluetooth setting to be enabled before the pairing can take place. You do not pair the device through your list of connected devices, simply power on the device and open the BACtrack application while Bluetooth is enabled and pairing will take place automatically upon opening the app.
For the BACtrack C6 and C8 devices, please make sure that it is set to App Mode or it will not connect to your smartphone and the results will only be displayed on the breathalyzer screen, not in the app.
To switch between the modes, once the device is off, hold the silver power button for 7 seconds until the screen displays App Mode.