When connecting multiple Midisport 2x2 Anniversary Edition or Midisport 4x4 Anniversary Edition devices to a Mac, Audio MIDI Setup (Macintosh HD>Applications>Utilities) will recognize all devices, but applications will not.  Simply rename the devices in  Audio MIDI Setup (while your MIDI software is closed), assigning each a unique name (e.g. "Midisport 2x2 1", "Midisport 2x2 2").  When you open your MIDI software, all Midisport devices should be available and working perfectly.