@ 6 am this morning, I'm in the garage tinkering with the wiper arm and following the instruction I got from the other forum. Now everything is working...took me only 15 mins

In case one of you run into this situation here's what the member told me:
Use something like a very small flathead screwdriver blade to pop/pry off the black cap that covers the wiper spindle. There's a slot on one edge where you can insert it. You will see a hex nut that secures the wiper arm to the rotating spindle. If it has backed off so far that the arm is not grabbing the splines, I suppose it would not rotate. If you are lucky, that may be all that is wrong, and you just need to re-seat the arm on the spindle and tighten the nut down. I think you need a 13mm socket.