I can't figure it out. I followed the instructions in this post
6 months ago and it worked perfectly on my 2011 MBP.
I did exactly the same a month ago and today and Aperture recognizes the M9 is attached, can actually trigger the camera from the laptop, but the shot count on the Aperture tether window remains at ZERO so the laptop gets no confirmation of a picture being taken. The camera is set to JPEG fine, B&W, PTP (the same settings which worked before).
I am not familiar with Aperture at all as I bought it mostly for the tethering capability. Are there specific settings in the program I need to set to get tethering to work?