It doesn't appear that M-Audio has released updated drivers for this device for Yosemite yet.
http://community.m-audio.com/m-audio/topics/yosemite-with-my-firewire-sole
There are some links there where people have gotten them working, but it requires manipulating some OS files and it's not something we can recommend or support here in this forum. Until updated drivers are available for the device, Audition is unlikely to be able to access the device.
