Have you checked your user preferences in the authoring ? Navigate to Project > User Preferences (or use shortcut Shift+U) and make sure the "Audio System" is set to "Detect" or "DirectSound".
Secondly, you need Microsoft Visual C++ to be able to use the authoring on Mac. If you think something went wrong during redistributable installation, you can perform these steps to make a clean install:
1- Close Wwise Authoring.
2- Delete your Wwise user preference folder located under ~/Library/Application Support/Wwise.
3- Make sure you have an internet connection.
4- Restart Wwise Authoring application, it will automatically download the "Microsoft Visual C++ Redistributable Setup" that will be installed on your Mac on a per user basis.
5- Click " I agree to the licence terms and condition " and proceed with Installation.
5- Wwise will be launched automatically upon completion of the "Microsoft Visual C++ Redistributable" installation.