Well, you can start troubleshooting by taking Audirvana out of the equation: Make sure it's closed (I believe it may have exclusive device control), then open Audio MIDI Setup in Applications/Utilities/ (part of every OS X install). With the WA7 properly connected, the options should look like this:
If this does NOT show the above, something's wrong with the USB connectivity to your WA7. If it does, something's wrong with your Audirvana setup. I personally use BitPerfect, and it works fine in Mavericks via USB3.
Edited by TheGrumpyOldMan - 7/2/14 at 1:27am