Maybe give your equipment a power cycle?
I know I have this weird thing with my DAC that whenever my iMac restarts, it doesn't recognize the DAC's USB port, so I turn off/on my DAC and it sees it again. However, when the computer is left on, I can unplug the USB cable in and out unlimited times and it works. When I shut down the iMac and boot it up, it recognizes the DAC fine. Just something about a restart.
Anyways, it can't hurt?