@combaindeft B) is clear, since the 3.3 regulator is on the FiPy device. Without that, no power at the 3.3V pin. Due to A) with the rock solid supply through a battery it is hard to accept, that it's a firmware issue, at least of the FiPy. Still, the PyTrack board can be the culprit. Did you try to run the FiPy without the PyTrack board, like on a breadboard with a separate USB/serial interface? Shorting 3.3 and GND should be avoided. P.S.: It's a pity that Pycom does not publish schematics.

@jcaron Thanks for the tip. Output below. from pytrack import Pytrack py = Pytrack() py.read_fw_version() 4 Which I think means it had flashed successfully (partly as my previously loaded libs had disappeared!). I had tried to connect the External I/O header as an alternative but had similar lack of luck. Tried High speed transfer both ticked and unticked based on reading another similar post. Just tried this again with same result. Flash tool states it is connecting... then shows a Failure! warning. The only COM port in the drop down is COM3 but I am not sure that's the attached PyTrack as removing the PyTrack from USB doesn't de-list the item listed in Device Manager. I am still concerned that it is more related to not having the correct Windows drivers in place that's preventing things from working as they should. Thanks again for the response. Regards Shaun