Hello Pilots,
We updated the game with a fix for issues related to OSX users being unable to start the game.
If you were affected by this error, please ensure that you have updated your game and try and launch the game again. If you encounter the same error, you may need to uninstall and reinstall the game.
If you continue to have issues after trying all the of the steps listed above, please let us know in the comments or in the discussions board here on Steam.