I'm completely new to both MacDive, Mac OS and my Oceanic OC1 (so I guess it's not much surprise I'm having "issues")

I've downloaded all the drivers for my Mac OS (just to be sure I got the right one) and they all said they installed fine. I plugged my OC1 into the USB port at the back of my Mac and got the usual countdown timer but no confirmation that a connection to a computer was detected.
I figured that wasn't a good thing but went ahead to see if I could download my dives anyway. After scanning for ports the only one that came up was "/dev/tty.usbserial-20030001" and when I tried to download the dives the following error came up:
Import Error
Failed connecting to dive computer on serial port '/dev/tty.usbserial-20030001' (Error Code: -6)
Is guess its hardly surprising as the OC1 never confirmed a connection but does anyone know what I'm doing wrong ....no doubt it's something trivial that I've overlooked but any help would be greatly appreciated.
Thanks!
Ziggy