error: Audition's primary temp volume cannot be found

This may have happened if you upgraded to MacOS Sierra, as I recently did. Could also happen if you use other tools to clear out temporary files on your disk.

The solution was simple: re-create the nested folder structure manually.

1. Open Audition
2. In the menu bar, choose Audition > Preferences > Media & Disk Cache
3. Note the location of Primary Temp. For me, it's /Users/username/Library/Caches/TemporaryItems/Adobe/Audition/7.0/
4. Obviously, username is whatever the username is for your Mac OS account
5. Open a new Finder window
6. In the menu bar, choose Go > Go to Folder...
7. Type in /Users/username/Library/Caches
8. Again, remember to change username to your Mac OS account's actual username
9. Create the rest of the nested folder structure manually, one at a time. For me, I created TemporaryItems, then opened it up and inside that created a folder called Adobe, then did the same process to create Audition, then finally 7.0.
10. Close and re-open Audition

I'm running Audition on a Macbook.

The best thing to do is to create it for yourself. On the main DAW I have one drive (solid state) reserved entirely for temp files - everything has a space for its own, and this works fine. The SSD is effectively a sacrificial drive - no permanent storage on it at all.