Need help with US cutter MH 871 usb/serial adapter

Can someone please give me a hand... Im having trouble with my MH 871 US cutter. I have an iMac OSX and im using signcut as my cutting software. It was cutting/working fine when all of a sudden it starts to freeze in the middle of the cut. I spoke with tech support and they told me to get a USB to serial adapter. After I got the adapter I couldnt reach tech support because they are closed on the weekends so I checked a few forums and tried to do it myself...FAIL...for some reason the usb connection wont show up in the output source only bluetooth. If someone could help I would really appreciate it, I have alot of orders on hold so I cant afford to wait on tech support.