The Uno Wifi Rev 2 board will not reliably connect to the USB on my Dell, whether in Windows or Ubuntu. The problem was seemingly random, but I finally figured out that if you unplug the aux power from the board then the USB will immediately connect. Replugging the power has no ill effect -- it just takes interrupting the power momentarily to make the USB work.
Does anyone know why and how to fix this? I am embedding the board in a unit, and for now I am running a power disconnect to where USB cables can be accessed for in-the-field reprogramming and/or debug ... a kludge I would rather not do. I figure something on the board must be wired wrong or missing, but it isn't obvious from the schematic (if I really have the right schematic for this board).