Greetings
I know this is an older question, but I recently encountered this exact issue during my first assignment in an Audio Design for Games class.
I, too, am a noob to the world of Wwise and video game sound design.
I'm using a Mac PowerBook, running High Sierra, and the Wwise version I am running is 2016.1.0.22.
I created a new project, for the Mac Platform only and cleared all the additional plug-ins at the bottom of the New Project screen and created my new project. I'll explain what I failed to change at this point that resulted in the inability to use the Play button inside of the Transport Control to preview.
With my new project created, Inside of the Actor-Mixer Hierarchy folder, under the Default Work Unit, I created a New Child Sound SFX. I located the audio file on my hard drive and selected the .wav file. At this point, if I hadn't verified that the file did import properly I would've never known. Nothing on screen warned me that I had done anything improperly. I was following a video archive that my professor had uploaded for me. I noticed my Play Button on the Transport Window was grey. Of course, when I clicked it, nothing happened.
It turns out, that when I created my new project, on the new project dialog, the default location showed c:\Filepath...\filename
My Mac doesn't use the c:\ file structure, and I doubt yours will either.
;^p
When creating a new project, make sure to choose a directory manually to ensure that the correct default directory path is populated accurately. I also had my audio files in this same directory.
I hope this helps someone.
James Trice