SoundManager.setup not running on IOS

Question

We have a web app that works fine on both PC (Windows, Linux, OSX) and Android but is not working on IOS. After lots of debugging, we've narrowed the cause down to the soundManager.setup function.

soundManager.setup({
    onready: function () {
        startGame();
    }
});

There a no console error messages, on IOS the startGame(); command just won't run (and our web app will keep loading). If I move the startGame() command out of the function like so:

startGame();
soundManager.setup({
    onready: function () {
        startGame();
    }
});

The game starts, but no sound is played.

Its an older codebase and I have very little experience with soundManager, so I was wondering if anyone here had run here into similar problems - and if so - how they managed to solve it.