I ran into this problem a year later, and found a solution.
The problem is that Audition CS versions are still 32-bit applications, not 64-bit.
Thus you must have the 32-bit versions of iZotope or any other VST plugins installed.
You can select these by re-running the installer.
Probably it’s ok to have the 64-bit versions installed also, if you need them for other music software.
Good fortune…