Had the same problem. You need delete the newer version of Wwise from you project and integrate the 2017.1.2 version instead.
- Close and save the Unreal/Wwise projects and Launcher
- Go into you Unreal projects folder, so find wherever your Unreal projects get saved and go into the folder of the project Wwise isn't working properly. For example my project is called "Jason_Demo"
- Once inside, go into the Plugins folder and delete the Wwise folder inside that.
- Reopen the Wwise launcher, click the unreal tab and you should have the option to integrate again.
- Press it and on the next screen you should see "Wwise Unreal Integration" Click the box just below it and select 2017.1.2
- Make any changes to Max Simultaneous Reverb Volumes or Wwise Project Path, if you did before, then integrate it.
Not sure why it does it, had a chat with a staff member and said they will have the integration team look into it.
Hopefully it will get fixed at some point, but the above is the only solution I found and worked for me.
You can test with a blank project if you want be cautious.