If you're using a Sonoff TH16 with a PCB reading version "2.1" or you bought your BierBot Brick, the update requires access to the COM-Headers on the PCB. In theory, the BierBot Bricks firmware runnning on your device would allow an update using the WiFi configuration portal. This, however, does not work, since the storage of the Sonoff TH 16 is too small to store both, the old software and the new software at the same time.