If a Kin firmware update fails, due to several reasons (lost Bluetooth connection, mobile phone ran out of battery, etc), there is a firmware recovery option inside the Settings menu on Trackunit Go called “Firmware Recovery”

Once inside, the Trackunit Go app will search for the Trackunit Kin tags that failed its firmware update as a list. You select which Trackunit Kin tag needs to recover its firmware, and Trackunit Go will try to update the firmware again.