Hey Thomas. Are you using perforce? I just ran into this issue, had already moved my soundbanks into the correct folders and still no sound in build. What we ended up doing was we checked out the entire Wwise project folder (not just the .wproj file) and the StreamingAsstets folder (Assets->StreamingAssets). We built with those checked out and everything works.
Due to an earlier error with a similar solution, I suspect that you could get away with just checking out the GeneratedSoundbanks folder (Assets->StreamingAssets->Audio->GeneratedSoundbanks) and the .cache folder inside your Wwise project folder. That may be worth a try.
You probably don't need this answer seeing as you asked your question in 2015, buuuut while faced with this issue I didn't find an answer, and this was the first thread that came up for me. I'm gonna leave this comment here for the next person who needs it.