Question RE: Mac does not detect Ayre QB-9 DAC

I returned from vacation and powered on my audio system. It seems my MAC computer is not detecting my Ayre QB-9 DAC. I go into system preferences, select sound and the Ayre QB-9 is not listed as an output. I called my dealer and they are checking but no answers yet.

I removed and reconnected the USB cable and still no QB-9. Everything worked pefectly before I powered down. A few software upgrades were made but nothing looked strange. I re-booted the MAC several times but the QB-9 is not in the list. It seems the MAC is not seeing the QB-9.

Someone at the store suggested maybe my USB cable has failed. Any suggestions?