Well if all of your python stuff is up to date hopefully thats all that was needed to get it connected.

After that its reinstalling any arduino drivers you might need, trying different usb ports on the mac, and trying a new usb cable... After that i dont know... If you have a non mac computer or laptop laying around try setting it up and see if it recognizes the printer that will narrow the issue to strictly being the usb cable which if you try another and it still doesnt work you have then narrowed it down to being the board itselfs usb connection and that is grounds for colin to replace the board and he will hes good like that.

Basically what i am saying is, use the process of elimination to rule out any and all possible causes for the printer and computer to not communicate. Once you do that you can with confidence tell colin everything you have done and there will be no doubt as to what the issue is. Hopefully... Because you will either eliminate all options to be the rumba board or you will eliminate all options to be your mac. Either or you will k ow whats going wrong and can take steps to fix the problem.