Hi there,
SO I too am awaiting my order of one unit. I see they come ready and pre configured as a media or sound device out of the box. Did you try that first?
when you connect a Xiao to it does the windows sound “new device found” sound?
smh on " ReSpeaker jtag windows serial port problem. ?
so does it show up in device manager like this:
So you flashed or tried to flash the reSpeaker USB port not the Xiao?
yes/no.
HTH
GL 
PJ 