The Phototrackr mini is compatible with Windows and Mac and its interface is USB, not serial. Try plugging it to another port and then check to see what happens. Normally, the device should be seen as a folder mounted on your desktop. The official specs say that the device is compatible with Mac. If it's not detected, then the problem might be with your MacBook. Try restarting it and then repeat the procedure. It should be detected afterwards.
