Don?t have a Winni but imagine they?re similar. I lost my transfer switch about a year ago. Ordered online and took about 3 days to receive expedited so that doesn?t help you. Shop gave me a hint if I was out on the road. First clearly mark your wires going to the switch. Then, with all power removed, swap the genset and shore power leads. That?s it. I believe most fail in the shore power position but it sounds like yours failed in the genset position (correct? you have no shore power but you do have power from the genset?). By swapping the shore leads to the other side (genset) you should get power. If you wanted genset power swap back to original position.
You could confirm what?s going on with a meter (be careful, this involves exposed high voltage leads). Remove the cover of your switch. Plug in to shore power. You should have voltage on the shore power lugs but no voltage at either the center or genset lugs. (Perhaps you?ve already done this.)